diff --git a/mps/code/arenacv.c b/mps/code/arenacv.c
index 62f6e788d70..e8b5788e8b9 100644
--- a/mps/code/arenacv.c
+++ b/mps/code/arenacv.c
@@ -339,8 +339,8 @@ static void testPageTable(ArenaClass class, Size size, Addr addr)
   Count tractsPerPage;
   
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, size);
-    MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, addr, addr);
+    MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size);
+    MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, addr);
     MPS_ARGS_DONE(args);
     die(ArenaCreate(&arena, class, args), "ArenaCreate");
   } MPS_ARGS_END(args);
@@ -378,7 +378,7 @@ static void testSize(Size size)
 
   do {
     MPS_ARGS_BEGIN(args) {
-      MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, size);
+      MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size);
       MPS_ARGS_DONE(args);
       res = ArenaCreate(&arena, class, args);
     } MPS_ARGS_END(args);
diff --git a/mps/code/cbs.c b/mps/code/cbs.c
index 14e13b51b01..250f69444de 100644
--- a/mps/code/cbs.c
+++ b/mps/code/cbs.c
@@ -1,7 +1,7 @@
 /* cbs.c: COALESCING BLOCK STRUCTURE IMPLEMENTATION
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  *
  * .intro: This is a portable implementation of coalescing block
  * structures.
@@ -287,8 +287,8 @@ Res CBSInit(Arena arena, CBS cbs, void *owner,
   SplayTreeInit(splayTreeOfCBS(cbs), &cbsSplayCompare,
                 fastFind ? &cbsUpdateNode : NULL);
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, MPS_KEY_MFS_UNIT_SIZE, size, sizeof(CBSBlockStruct));
-    MPS_ARGS_ADD(args, MPS_KEY_EXTEND_BY, size, sizeof(CBSBlockStruct) * 64);
+    MPS_ARGS_ADD(args, MPS_KEY_MFS_UNIT_SIZE, sizeof(CBSBlockStruct));
+    MPS_ARGS_ADD(args, MPS_KEY_EXTEND_BY, sizeof(CBSBlockStruct) * 64);
     MPS_ARGS_DONE(args);
     res = PoolCreate(&(cbs->blockPool), arena, PoolClassMFS(), args);
   } MPS_ARGS_END(args);
@@ -1658,7 +1658,7 @@ Res CBSDescribe(CBS cbs, mps_lib_FILE *stream)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/dbgpool.c b/mps/code/dbgpool.c
index 88dec0532b6..3d670d8d361 100644
--- a/mps/code/dbgpool.c
+++ b/mps/code/dbgpool.c
@@ -1,7 +1,7 @@
 /* dbgpool.c: POOL DEBUG MIXIN
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  *
  * .source: design.mps.object-debug
@@ -186,8 +186,8 @@ static Res DebugPoolInit(Pool pool, ArgList args)
     /* This pool has to be like the arena control pool: the blocks */
     /* allocated must be accessible using void*. */
     MPS_ARGS_BEGIN(pcArgs) {
-      MPS_ARGS_ADD(pcArgs, MPS_KEY_EXTEND_BY, size, debug->tagSize); /* FIXME: Check this */
-      MPS_ARGS_ADD(pcArgs, MPS_KEY_MFS_UNIT_SIZE, size, debug->tagSize);
+      MPS_ARGS_ADD(pcArgs, MPS_KEY_EXTEND_BY, debug->tagSize); /* FIXME: Check this */
+      MPS_ARGS_ADD(pcArgs, MPS_KEY_MFS_UNIT_SIZE, debug->tagSize);
       MPS_ARGS_DONE(pcArgs);
       res = PoolCreate(&debug->tagPool, PoolArena(pool), PoolClassMFS(), pcArgs);
     } MPS_ARGS_END(pcArgs);
@@ -687,7 +687,7 @@ void PoolClassMixInDebug(PoolClass class)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mps.h b/mps/code/mps.h
index 8bf1ee9ce1a..67d1f77738c 100644
--- a/mps/code/mps.h
+++ b/mps/code/mps.h
@@ -1,7 +1,7 @@
 /* mps.h: RAVENBROOK MEMORY POOL SYSTEM C INTERFACE
  *
  * $Id$
- * Copyright (c) 2001-2012 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (c) 2002 Global Graphics Software.
  *
  * THIS HEADER IS NOT DOCUMENTATION.
@@ -123,26 +123,36 @@ extern mps_arg_s mps_args_none[];
 
 extern const struct mps_key_s _mps_key_arena_size;
 #define MPS_KEY_ARENA_SIZE      (&_mps_key_arena_size)
+#define MPS_KEY_ARENA_SIZE_FIELD() size
 extern const struct mps_key_s _mps_key_format;
 #define MPS_KEY_FORMAT          (&_mps_key_format)
+#define MPS_KEY_FORMAT_FIELD()    format
 extern const struct mps_key_s _mps_key_chain;
 #define MPS_KEY_CHAIN           (&_mps_key_chain)
+#define MPS_KEY_CHAIN_FIELD()     chain
 extern const struct mps_key_s _mps_key_rank;
-#define MPS_KEY_RANK (&_mps_key_rank)
+#define MPS_KEY_RANK            (&_mps_key_rank)
+#define MPS_KEY_RANK_FIELD()      rank
 
 extern const struct mps_key_s _mps_key_extend_by;
 #define MPS_KEY_EXTEND_BY       (&_mps_key_extend_by)
+#define MPS_KEY_EXTEND_BY_FIELD() size
 extern const struct mps_key_s _mps_key_min_size;
 #define MPS_KEY_MIN_SIZE        (&_mps_key_min_size)
+#define MPS_KEY_MIN_SIZE_FIELD()  size
 extern const struct mps_key_s _mps_key_mean_size;
 #define MPS_KEY_MEAN_SIZE       (&_mps_key_mean_size)
+#define MPS_KEY_MEAN_SIZE_FIELD() size
 extern const struct mps_key_s _mps_key_max_size;
 #define MPS_KEY_MAX_SIZE        (&_mps_key_max_size)
+#define MPS_KEY_MAX_SIZE_FIELD()  size
 extern const struct mps_key_s _mps_key_align;
 #define MPS_KEY_ALIGN           (&_mps_key_align)
+#define MPS_KEY_ALIGN_FIELD()     align
 
 extern const struct mps_key_s _mps_key_vmw3_top_down;
 #define MPS_KEY_VMW3_TOP_DOWN   (&_mps_key_vmw3_top_down)
+#define MPS_KEY_VMW3_TOP_DOWN_FIELD() b
 
 /* Maximum length of a keyword argument list. */
 #define MPS_ARGS_MAX          32
@@ -153,25 +163,30 @@ extern const struct mps_key_s _mps_key_vmw3_top_down;
       unsigned _var##_i = 0; \
       BEGIN
 
-#define MPS_ARGS_ADD(_var, _key, _field, _val) \
+#define MPS_ARGS_ADD_FIELD(_var, _key, _field, _val)  \
   BEGIN \
-    /* TODO: AVER(_var_i < MPS_ARGS_MAX); */ \
+    AVER(_var##_i < MPS_ARGS_MAX); \
     _var[_var##_i].key = (_key); \
     _var[_var##_i].val._field = (_val); \
     ++_var##_i; \
   END
 
+#define MPS_ARGS_ADD(_var, _key, _val) \
+  MPS_ARGS_ADD_FIELD(_var, _key, _key##_FIELD(), _val)
+
 #define MPS_ARGS_DONE(_var) \
   BEGIN \
-    /* TODO: AVER(_var##_i < MPS_ARGS_MAX); */ \
+    AVER(_var##_i < MPS_ARGS_MAX); \
     _var[_var##_i].key = MPS_KEY_ARGS_END; \
-    /* TODO: _var##_i = MPS_ARGS_MAX; */ \
+    _var##_i = MPS_ARGS_MAX; \
   END
 
 #define MPS_ARGS_END(_var) \
     END; \
   END
 
+#define MPS_ARG(_key, _val) ((mps_arg_s){(_key), {._key##_FIELD() = (_val)}})
+
 
 /* <a id="message.types"> Keep in sync with
  * <code/mpmtypes.h#message.types> */
@@ -690,6 +705,7 @@ typedef struct mps_pool_debug_option_s {
 
 extern const struct mps_key_s _mps_key_pool_debug_options;
 #define MPS_KEY_POOL_DEBUG_OPTIONS (&_mps_key_pool_debug_options)
+#define MPS_KEY_VAL_POOL_DEBUG_OPTIONS pool_debug_options
 
 extern void mps_pool_check_fenceposts(mps_pool_t);
 extern void mps_pool_check_free_space(mps_pool_t);
@@ -740,7 +756,7 @@ extern mps_res_t _mps_fix2(mps_ss_t, mps_addr_t *);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002, 2008 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpsacl.h b/mps/code/mpsacl.h
index ec7a21c027a..10f2bddf581 100644
--- a/mps/code/mpsacl.h
+++ b/mps/code/mpsacl.h
@@ -1,7 +1,7 @@
 /* mpsacl.h: MEMORY POOL SYSTEM ARENA CLASS "CL"
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #ifndef mpsacl_h
@@ -12,6 +12,7 @@
 /* Client arena base address argument */
 extern const struct mps_key_s _mps_key_arena_cl_addr;
 #define MPS_KEY_ARENA_CL_ADDR (&_mps_key_arena_cl_addr)
+#define MPS_KEY_ARENA_CL_ADDR_FIELD() addr
 
 extern mps_arena_class_t mps_arena_class_cl(void);
 
@@ -21,7 +22,7 @@ extern mps_arena_class_t mps_arena_class_cl(void);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpscams.h b/mps/code/mpscams.h
index f8013467a5d..f410c2734dd 100644
--- a/mps/code/mpscams.h
+++ b/mps/code/mpscams.h
@@ -1,7 +1,7 @@
 /* mpscams.h: MEMORY POOL SYSTEM CLASS "AMS"
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  */
 
@@ -12,6 +12,7 @@
 
 extern const struct mps_key_s _mps_key_ams_support_ambiguous;
 #define MPS_KEY_AMS_SUPPORT_AMBIGUOUS (&_mps_key_ams_support_ambiguous)
+#define MPS_KEY_AMS_SUPPORT_AMBIGUOUS_FIELD() b
 
 extern mps_class_t mps_class_ams(void);
 extern mps_class_t mps_class_ams_debug(void);
@@ -21,7 +22,7 @@ extern mps_class_t mps_class_ams_debug(void);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpscawl.h b/mps/code/mpscawl.h
index a332c5057f1..5271560b11f 100644
--- a/mps/code/mpscawl.h
+++ b/mps/code/mpscawl.h
@@ -1,7 +1,7 @@
 /* mpscaawl.h: MEMORY POOL SYSTEM CLASS "AWL"
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #ifndef mpscawl_h
@@ -11,6 +11,7 @@
 
 extern const struct mps_key_s _mps_key_awl_find_dependent;
 #define MPS_KEY_AWL_FIND_DEPENDENT (&_mps_key_awl_find_dependent)
+#define MPS_KEY_AWL_FIND_DEPENDENT_FIELD() addr_method
 
 extern mps_class_t mps_class_awl(void);
 
@@ -21,7 +22,7 @@ typedef mps_addr_t (*mps_awl_find_dependent_t)(mps_addr_t addr);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpscmfs.h b/mps/code/mpscmfs.h
index 734fa766d14..87f6e108424 100644
--- a/mps/code/mpscmfs.h
+++ b/mps/code/mpscmfs.h
@@ -1,7 +1,7 @@
 /* mpscamfs.h: MEMORY POOL SYSTEM CLASS "MFS"
  *
  * $Id$
- * Copyright (c) 2001-2012 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #ifndef mpscmfs_h
@@ -11,6 +11,7 @@
 
 extern const struct mps_key_s _mps_key_mfs_unit_size;
 #define MPS_KEY_MFS_UNIT_SIZE (&_mps_key_mfs_unit_size)
+#define MPS_KEY_MFS_UNIT_SIZE_FIELD() size
 
 extern mps_class_t mps_class_mfs(void);
 
@@ -19,7 +20,7 @@ extern mps_class_t mps_class_mfs(void);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2012 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpscmvff.h b/mps/code/mpscmvff.h
index 6b13af35a22..09164872b76 100644
--- a/mps/code/mpscmvff.h
+++ b/mps/code/mpscmvff.h
@@ -1,7 +1,7 @@
 /* mpscmvff.h: MEMORY POOL SYSTEM CLASS "MVFF"
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #ifndef mpscmvff_h
@@ -11,10 +11,13 @@
 
 extern const struct mps_key_s _mps_key_mvff_slot_high;
 #define MPS_KEY_MVFF_SLOT_HIGH (&_mps_key_mvff_slot_high)
+#define MPS_KEY_MVFF_SLOT_HIGH_FIELD() b
 extern const struct mps_key_s _mps_key_mvff_arena_high;
 #define MPS_KEY_MVFF_ARENA_HIGH (&_mps_key_mvff_arena_high)
+#define MPS_KEY_MVFF_ARENA_HIGH_FIELD() b
 extern const struct mps_key_s _mps_key_mvff_first_fit;
 #define MPS_KEY_MVFF_FIRST_FIT (&_mps_key_mvff_first_fit)
+#define MPS_KEY_MVFF_FIRST_FIT_FIELD() b
 
 extern size_t mps_mvff_free_size(mps_pool_t mps_pool);
 extern size_t mps_mvff_size(mps_pool_t mps_pool);
@@ -26,7 +29,7 @@ extern mps_class_t mps_class_mvff_debug(void);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/mpscmvt.h b/mps/code/mpscmvt.h
index b02c6173fb1..2237639310b 100644
--- a/mps/code/mpscmvt.h
+++ b/mps/code/mpscmvt.h
@@ -1,7 +1,7 @@
 /* mpscmvt.h: MEMORY POOL SYSTEM CLASS "MVT"
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #ifndef mpscmvt_h
@@ -11,8 +11,10 @@
 
 extern const struct mps_key_s _mps_key_mvt_reserve_depth;
 #define MPS_KEY_MVT_RESERVE_DEPTH (&_mps_key_mvt_reserve_depth)
+#define MPS_KEY_MVT_RESERVE_DEPTH_FIELD() count
 extern const struct mps_key_s _mps_key_mvt_frag_limit;
 #define MPS_KEY_MVT_FRAG_LIMIT (&_mps_key_mvt_frag_limit)
+#define MPS_KEY_MVT_FRAG_LIMIT_FIELD() count
 
 /* The mvt pool class has five extra parameters to mps_pool_create:
  *  mps_res_t mps_pool_create(mps_pool_t * pool, mps_arena_t arena,
@@ -42,7 +44,7 @@ extern size_t mps_mvt_size(mps_pool_t mps_pool);
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index 59c4453c4ff..874b01b2b5d 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -1,7 +1,7 @@
 /* poolamc.c: AUTOMATIC MOSTLY-COPYING MEMORY POOL CLASS
  *
  * $Id$
- * Copyright (c) 2001-2012 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  *
  * .sources: <design/poolamc/>.
@@ -1171,7 +1171,7 @@ static Res AMCBufferFill(Addr *baseReturn, Addr *limitReturn,
   genNr = PoolGenNr(&gen->pgen);
   SegPrefExpress(&segPrefStruct, SegPrefGen, &genNr);
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, amcKeySegType, p, &gen->type); /* .segtype */
+    MPS_ARGS_ADD_FIELD(args, amcKeySegType, p, &gen->type); /* .segtype */
     MPS_ARGS_DONE(args);
     res = SegAlloc(&seg, amcSegClassGet(), &segPrefStruct,
                    alignedSize, pool, withReservoirPermit, args);
@@ -2556,7 +2556,7 @@ static Bool AMCCheck(AMC amc)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2012 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/poolawl.c b/mps/code/poolawl.c
index 3014376a8eb..e77256ee236 100644
--- a/mps/code/poolawl.c
+++ b/mps/code/poolawl.c
@@ -1,7 +1,7 @@
 /* poolawl.c: AUTOMATIC WEAK LINKED POOL CLASS
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  *
  *
  * DESIGN
@@ -474,7 +474,7 @@ static Res AWLSegCreate(AWLSeg *awlsegReturn,
   SegPrefExpress(&segPrefStruct, SegPrefCollected, NULL);
   SegPrefExpress(&segPrefStruct, SegPrefGen, &awl->gen);
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, awlKeySegRankSet, u, rankSet);
+    MPS_ARGS_ADD_FIELD(args, awlKeySegRankSet, u, rankSet);
     MPS_ARGS_DONE(args);
     res = SegAlloc(&seg, AWLSegClassGet(), &segPrefStruct, size, pool,
                    reservoirPermit, args);
@@ -1316,7 +1316,7 @@ static Bool AWLCheck(AWL awl)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/poolmrg.c b/mps/code/poolmrg.c
index fc93cc47d0b..b7cf9794361 100644
--- a/mps/code/poolmrg.c
+++ b/mps/code/poolmrg.c
@@ -1,7 +1,7 @@
 /* poolmrg.c: MANUAL RANK GUARDIAN POOL
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  * 
  * 
@@ -525,7 +525,7 @@ static Res MRGSegPairCreate(MRGRefSeg *refSegReturn, MRG mrg,
   linkseg = Seg2LinkSeg(segLink);
   
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, mrgKeyLinkSeg, p, linkseg); /* .ref.initarg */
+    MPS_ARGS_ADD_FIELD(args, mrgKeyLinkSeg, p, linkseg); /* .ref.initarg */
     MPS_ARGS_DONE(args);
     res = SegAlloc(&segRefPart, EnsureMRGRefSegClass(),
                    SegPrefDefault(), mrg->extendBy, pool,
@@ -877,7 +877,7 @@ PoolClass PoolClassMRG(void)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/poolmv.c b/mps/code/poolmv.c
index e827e9d69b6..812d3099266 100644
--- a/mps/code/poolmv.c
+++ b/mps/code/poolmv.c
@@ -1,7 +1,7 @@
 /* poolmv.c: MANUAL VARIABLE POOL
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  *
  * **** RESTRICTION: This pool may not allocate from the arena control
@@ -241,8 +241,8 @@ static Res MVInit(Pool pool, ArgList args)
   }
 
   MPS_ARGS_BEGIN(piArgs) {
-    MPS_ARGS_ADD(piArgs, MPS_KEY_EXTEND_BY, size, blockExtendBy);
-    MPS_ARGS_ADD(piArgs, MPS_KEY_MFS_UNIT_SIZE, size, sizeof(MVBlockStruct));
+    MPS_ARGS_ADD(piArgs, MPS_KEY_EXTEND_BY, blockExtendBy);
+    MPS_ARGS_ADD(piArgs, MPS_KEY_MFS_UNIT_SIZE, sizeof(MVBlockStruct));
     MPS_ARGS_DONE(piArgs);
     res = PoolInit(&mv->blockPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
   } MPS_ARGS_END(piArgs);
@@ -252,8 +252,8 @@ static Res MVInit(Pool pool, ArgList args)
   spanExtendBy = sizeof(MVSpanStruct) * (maxSize/extendBy);
 
   MPS_ARGS_BEGIN(piArgs) {
-    MPS_ARGS_ADD(piArgs, MPS_KEY_EXTEND_BY, size, spanExtendBy);
-    MPS_ARGS_ADD(piArgs, MPS_KEY_MFS_UNIT_SIZE, size, sizeof(MVSpanStruct));
+    MPS_ARGS_ADD(piArgs, MPS_KEY_EXTEND_BY, spanExtendBy);
+    MPS_ARGS_ADD(piArgs, MPS_KEY_MFS_UNIT_SIZE, sizeof(MVSpanStruct));
     MPS_ARGS_DONE(piArgs);
     res = PoolInit(&mv->spanPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
   } MPS_ARGS_END(piArgs);
@@ -903,7 +903,7 @@ Bool MVCheck(MV mv)
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  * 
diff --git a/mps/code/poolncv.c b/mps/code/poolncv.c
index c250e84d2cd..ef0b67eb75e 100644
--- a/mps/code/poolncv.c
+++ b/mps/code/poolncv.c
@@ -1,7 +1,7 @@
 /* poolncv.c: NULL POOL COVERAGE TEST
  *
  *  $Id$
- *  Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ *  Copyright (c) 2001-2013 Ravenbrook Limited.  See end of file for license.
  */
 
 #include "mpm.h"
@@ -34,7 +34,7 @@ int main(int argc, char *argv[])
 {
   testlib_unused(argc);
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, 600000);
+    MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, 600000);
     MPS_ARGS_DONE(args);
     testit((ArenaClass)mps_arena_class_vm(), args);
   } MPS_ARGS_END(args);
diff --git a/mps/code/segsmss.c b/mps/code/segsmss.c
index 8708db2348d..90269aa2abb 100644
--- a/mps/code/segsmss.c
+++ b/mps/code/segsmss.c
@@ -765,7 +765,7 @@ static void *test(void *arg, size_t s)
   die(mps_fmt_create_A(&format, arena, dylan_fmt_A()), "fmt_create");
 
   MPS_ARGS_BEGIN(args) {
-    MPS_ARGS_ADD(args, MPS_KEY_FORMAT, format, format);
+    MPS_ARGS_ADD(args, MPS_KEY_FORMAT, format);
     MPS_ARGS_DONE(args);
     die(mps_pool_create_k(&pool, arena, mps_class_amst(), args),
         "pool_create(amst)");
diff --git a/mps/example/scheme/scheme-advanced.c b/mps/example/scheme/scheme-advanced.c
index 2c86aade2dd..a006f156de8 100644
--- a/mps/example/scheme/scheme-advanced.c
+++ b/mps/example/scheme/scheme-advanced.c
@@ -4471,7 +4471,7 @@ int main(int argc, char *argv[])
   /* Create an MPS arena.  There is usually only one of these in a process.
      It holds all the MPS "global" state and is where everything happens. */
   res = mps_arena_create_k(&arena, mps_arena_class_vm(), 
-         (mps_arg_s[]){{MPS_KEY_ARENA_SIZE, .val.size = 32 * 1024 * 1024},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_SIZE, 32 * 1024 * 1024),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create arena");
 
@@ -4489,8 +4489,8 @@ int main(int argc, char *argv[])
   /* Create an Automatic Mostly-Copying (AMC) pool to manage the Scheme
      objects.  This is a kind of copying garbage collector. */
   res = mps_pool_create_k(&obj_pool, arena, mps_class_amc(),
-         (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = obj_chain},
-                       {MPS_KEY_FORMAT, .val.format = obj_fmt},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, obj_chain),
+                       MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create obj pool");
 
@@ -4504,8 +4504,8 @@ int main(int argc, char *argv[])
   /* Create an Automatic Mostly-Copying Zero-rank (AMCZ) pool to
      manage the leaf objects. */
   res = mps_pool_create_k(&leaf_pool, arena, mps_class_amcz(),
-         (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = obj_chain},
-                       {MPS_KEY_FORMAT, .val.format = obj_fmt},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, obj_chain),
+                       MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create leaf pool");
 
@@ -4520,19 +4520,19 @@ int main(int argc, char *argv[])
   /* Create an Automatic Weak Linked (AWL) pool to manage the hash table
      buckets. */
   res = mps_pool_create_k(&buckets_pool, arena, mps_class_awl(),
-         (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = buckets_fmt},
-                       {MPS_KEY_AWL_FIND_DEPENDENT,
-                           .val.addr_method = buckets_find_dependent},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, buckets_fmt),
+                       MPS_ARG(MPS_KEY_AWL_FIND_DEPENDENT,
+                               buckets_find_dependent),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create buckets pool");
 
   /* Create allocation points for weak and strong buckets. */
   res = mps_ap_create_k(&strong_buckets_ap, buckets_pool,
-         (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_exact()},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_exact()),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create strong buckets allocation point");
   res = mps_ap_create_k(&weak_buckets_ap, buckets_pool,
-         (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_weak()},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_weak()),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create weak buckets allocation point");
 
diff --git a/mps/example/scheme/scheme.c b/mps/example/scheme/scheme.c
index 2bac9c0042d..527d946b9e8 100644
--- a/mps/example/scheme/scheme.c
+++ b/mps/example/scheme/scheme.c
@@ -4392,7 +4392,7 @@ int main(int argc, char *argv[])
   /* Create an MPS arena.  There is usually only one of these in a process.
      It holds all the MPS "global" state and is where everything happens. */
   res = mps_arena_create_k(&arena, mps_arena_class_vm(), 
-         (mps_arg_s[]){{MPS_KEY_ARENA_SIZE, .val.size = 32 * 1024 * 1024},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_SIZE, 32 * 1024 * 1024),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create arena");
 
@@ -4410,8 +4410,8 @@ int main(int argc, char *argv[])
   /* Create an Automatic Mostly-Copying (AMC) pool to manage the Scheme
      objects.  This is a kind of copying garbage collector. */
   res = mps_pool_create_k(&obj_pool, arena, mps_class_amc(),
-         (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = obj_chain},
-                       {MPS_KEY_FORMAT, .val.format = obj_fmt},
+         (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, obj_chain),
+                       MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                        {MPS_KEY_ARGS_END}});
   if (res != MPS_RES_OK) error("Couldn't create obj pool");
 
diff --git a/mps/manual/source/guide/advanced.rst b/mps/manual/source/guide/advanced.rst
index 7ab02a3141d..7ef3a7bea3d 100644
--- a/mps/manual/source/guide/advanced.rst
+++ b/mps/manual/source/guide/advanced.rst
@@ -713,7 +713,7 @@ Finally, we can create the buckets pool and its allocation points::
     /* Create an Automatic Weak Linked (AWL) pool to manage the hash table
        buckets. */
     res = mps_pool_create_k(&buckets_pool, arena, mps_class_awl(),
-           (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = buckets_fmt},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, buckets_fmt),
                          {MPS_KEY_AWL_FIND_DEPENDENT,
                              .val.addr_method = buckets_find_dependent},
                          {MPS_KEY_ARGS_END}});
@@ -721,11 +721,11 @@ Finally, we can create the buckets pool and its allocation points::
 
     /* Create allocation points for weak and strong buckets. */
     res = mps_ap_create_k(&strong_buckets_ap, buckets_pool,
-           (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_exact()},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_exact()),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create strong buckets allocation point");
     res = mps_ap_create_k(&weak_buckets_ap, buckets_pool,
-           (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_weak()},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_weak()),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create weak buckets allocation point");
 
@@ -893,8 +893,8 @@ Second, the leaf objects must be allocated on ``leaf_ap`` instead of
     /* Create an Automatic Mostly-Copying Zero-rank (AMCZ) pool to
        manage the leaf objects. */
     res = mps_pool_create_k(&leaf_pool, arena, mps_class_amcz(),
-           (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = obj_chain},
-                         {MPS_KEY_FORMAT, .val.format = obj_fmt},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, obj_chain),
+                         MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create leaf pool");
 
diff --git a/mps/manual/source/guide/lang.rst b/mps/manual/source/guide/lang.rst
index edaee742830..d6d8943cabc 100644
--- a/mps/manual/source/guide/lang.rst
+++ b/mps/manual/source/guide/lang.rst
@@ -176,7 +176,7 @@ Let's reserve 32 megabytes::
 
     mps_res_t res;
     res = mps_arena_create_k(&arena, mps_arena_class_vm(), 
-           (mps_arg_s[]){{MPS_KEY_ARENA_SIZE, .val.size = 32 * 1024 * 1024},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_SIZE, 32 * 1024 * 1024),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create arena");
 
@@ -771,8 +771,8 @@ And finally the :term:`pool`::
 
     mps_pool_t obj_pool;
     res = mps_pool_create_k(&obj_pool, arena, mps_class_amc(),
-           (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = obj_chain},
-                         {MPS_KEY_FORMAT, .val.format = obj_fmt},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, obj_chain),
+                         MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create obj pool");
 
diff --git a/mps/manual/source/pool/amc.rst b/mps/manual/source/pool/amc.rst
index 7c6c9927aec..376f22752cd 100644
--- a/mps/manual/source/pool/amc.rst
+++ b/mps/manual/source/pool/amc.rst
@@ -103,22 +103,20 @@ AMC interface
     When creating an AMC pool, :c:func:`mps_pool_create_k` requires
     two :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a
-      :term:`scan method`, a :term:`skip method`, a :term:`forward
-      method`, an :term:`is-forwarded method` and a :term:`padding
-      method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`scan method`, a :term:`skip
+      method`, a :term:`forward method`, an :term:`is-forwarded
+      method` and a :term:`padding method`.
 
-    * :c:macro:`MPS_KEY_CHAIN` (member ``.val.chain``; type
-      :c:type:`mps_chain_t`) specifies the :term:`generation chain`
-      for the pool.
+    * :c:macro:`MPS_KEY_CHAIN` (type :c:type:`mps_chain_t`) specifies
+      the :term:`generation chain` for the pool.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_amc(),
-               (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = chain},
-                             {MPS_KEY_FORMAT, .val.format = fmt},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, chain),
+                             MPS_ARG(MPS_KEY_FORMAT, fmt),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/amcz.rst b/mps/manual/source/pool/amcz.rst
index c3a01202532..d2cac80ca1e 100644
--- a/mps/manual/source/pool/amcz.rst
+++ b/mps/manual/source/pool/amcz.rst
@@ -62,21 +62,20 @@ AMCZ interface
     When creating an AMCZ pool, :c:func:`mps_pool_create_k` requires
     two :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a
-      :term:`skip method`, a :term:`forward method`, an
-      :term:`is-forwarded method` and a :term:`padding method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`skip method`, a :term:`forward
+      method`, an :term:`is-forwarded method` and a :term:`padding
+      method`.
 
-    * :c:macro:`MPS_KEY_CHAIN` (member ``.val.chain``; type
-      :c:type:`mps_chain_t`) specifies the :term:`generation chain`
-      for the pool.
+    * :c:macro:`MPS_KEY_CHAIN` (type :c:type:`mps_chain_t`) specifies
+      the :term:`generation chain` for the pool.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_amcz(),
-               (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = chain},
-                             {MPS_KEY_FORMAT, .val.format = fmt},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, chain),
+                             MPS_ARG(MPS_KEY_FORMAT, fmt),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/ams.rst b/mps/manual/source/pool/ams.rst
index 0e9cac244c6..523ac6d5d2e 100644
--- a/mps/manual/source/pool/ams.rst
+++ b/mps/manual/source/pool/ams.rst
@@ -106,20 +106,20 @@ AMS interface
     When creating an AMS pool, :c:func:`mps_pool_create_k` requires
     two :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a
-      :term:`scan method` and a :term:`skip method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`scan method` and a :term:`skip
+      method`.
 
-    * :c:macro:`MPS_KEY_CHAIN` (member ``.val.chain``; type
-      :c:type:`mps_chain_t`) specifies the :term:`generation chain`
-      for the pool. It must have a single generation.
+    * :c:macro:`MPS_KEY_CHAIN` (type :c:type:`mps_chain_t`) specifies
+      the :term:`generation chain` for the pool. It must have a single
+      generation.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_ams(),
-               (mps_arg_s[]){{MPS_KEY_CHAIN, .val.chain = chain},
-                             {MPS_KEY_FORMAT, .val.format = fmt},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_CHAIN, chain),
+                             MPS_ARG(MPS_KEY_FORMAT, fmt),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/awl.rst b/mps/manual/source/pool/awl.rst
index 61bbd202eed..a5379c321f1 100644
--- a/mps/manual/source/pool/awl.rst
+++ b/mps/manual/source/pool/awl.rst
@@ -321,21 +321,21 @@ AWL interface
     When creating an AWL pool, :c:func:`mps_pool_create_k` requires
     two :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a :term:`scan
-      method` and a :term:`skip method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`scan method` and a :term:`skip
+      method`.
 
-    * :c:macro:`MPS_KEY_AWL_FIND_DEPENDENT` (member
-      ``.val.addr_method``; type :c:type:`mps_awl_find_dependent_t`)
-      is a function that specifies how to find the :term:`dependent
-      object` for an object in the pool.
+    * :c:macro:`MPS_KEY_AWL_FIND_DEPENDENT` (type
+      :c:type:`mps_awl_find_dependent_t`) is a function that specifies
+      how to find the :term:`dependent object` for an object in the
+      pool.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_awl(),
-               (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = fmt},
-                             {MPS_KEY_AWL_FIND_DEPENDENT, .val.addr_method = find_dependent},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, fmt),
+                             MPS_ARG(MPS_KEY_AWL_FIND_DEPENDENT, find_dependent),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
@@ -351,18 +351,17 @@ AWL interface
     When creating an :term:`allocation point` on an AWL pool,
     :c:func:`mps_ap_create_k` requires one keyword argument:
 
-    * :c:macro:`MPS_KEY_RANK` (member ``.val.rank``; type
-      :c:type:`mps_rank_t`) specifies the :term:`rank` of references
-      in objects allocated on this allocation point. It must be
-      :c:func:`mps_rank_exact` (if the objects allocated on this
-      allocation point will contain :term:`exact references`), or
-      :c:func:`mps_rank_weak` (if the objects will contain :term:`weak
-      references (1)`).
+    * :c:macro:`MPS_KEY_RANK` (type :c:type:`mps_rank_t`) specifies
+      the :term:`rank` of references in objects allocated on this
+      allocation point. It must be :c:func:`mps_rank_exact` (if the
+      objects allocated on this allocation point will contain
+      :term:`exact references`), or :c:func:`mps_rank_weak` (if the
+      objects will contain :term:`weak references (1)`).
 
     For example, in :term:`C99`::
 
         res = mps_ap_create_k(&ap, awl_pool,
-               (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_weak()},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_weak()),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/lo.rst b/mps/manual/source/pool/lo.rst
index dad1997a4a1..f826d26b292 100644
--- a/mps/manual/source/pool/lo.rst
+++ b/mps/manual/source/pool/lo.rst
@@ -108,15 +108,14 @@ LO interface
     When creating an LO pool, :c:func:`mps_pool_create_k` require one
     :term:`keyword argument`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a :term:`skip
-      method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`skip method`.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_lo(),
-               (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = fmt},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, fmt),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/mfs.rst b/mps/manual/source/pool/mfs.rst
index 9c6bf500f7d..d6aa1273907 100644
--- a/mps/manual/source/pool/mfs.rst
+++ b/mps/manual/source/pool/mfs.rst
@@ -80,24 +80,22 @@ MFS interface
     When creating an MFS pool, :c:func:`mps_pool_create_k` requires
     two :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_MFS_UNIT_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the :term:`size` of blocks that will be
-      allocated from this pool, in :term:`bytes (1)`. It must be at
-      least one :term:`word`.
+    * :c:macro:`MPS_KEY_MFS_UNIT_SIZE` (type :c:type:`size_t`) is the
+      :term:`size` of blocks that will be allocated from this pool, in
+      :term:`bytes (1)`. It must be at least one :term:`word`.
 
-    * :c:macro:`MPS_KEY_EXTEND_BY` (member ``.val.size``; type
-      :c:type:`size_t`) is the :term:`size` of segment that the pool
-      will request from the :term:`arena`. It must be at least as big
-      as the unit size specified by the
-      :c:macro:`MPS_KEY_MFS_UNIT_SIZE` keyword argument. If this is
-      not a multiple of the unit size, there will be wasted space in
-      each segment.
+    * :c:macro:`MPS_KEY_EXTEND_BY` (type :c:type:`size_t`) is the
+      :term:`size` of segment that the pool will request from the
+      :term:`arena`. It must be at least as big as the unit size
+      specified by the :c:macro:`MPS_KEY_MFS_UNIT_SIZE` keyword
+      argument. If this is not a multiple of the unit size, there will
+      be wasted space in each segment.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_mfs(),
-               (mps_arg_s[]){{MPS_KEY_MFS_UNIT_SIZE, .val.size = 1024},
-                             {MPS_KEY_EXTEND_BY, .val.size = 1024 * 1024},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_MFS_UNIT_SIZE, 1024),
+                             MPS_ARG(MPS_KEY_EXTEND_BY, 1024 * 1024),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/mv.rst b/mps/manual/source/pool/mv.rst
index dccb5abe0ee..815534e7934 100644
--- a/mps/manual/source/pool/mv.rst
+++ b/mps/manual/source/pool/mv.rst
@@ -75,17 +75,17 @@ MV interface
     When creating an MV pool, :c:func:`mps_pool_create_k` requires
     three :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_EXTEND_BY` (member ``.val.size``; type
-      :c:type:`size_t`) is the :term:`size` of segment that the pool
-      will request from the :term:`arena`.
+    * :c:macro:`MPS_KEY_EXTEND_BY` (type :c:type:`size_t`) is the
+      :term:`size` of segment that the pool will request from the
+      :term:`arena`.
 
-    * :c:macro:`MPS_KEY_MEAN_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted mean size of blocks that
-      will be allocated from the pool.
+    * :c:macro:`MPS_KEY_MEAN_SIZE` (type :c:type:`size_t`) is the
+      predicted mean size of blocks that will be allocated from the
+      pool.
 
-    * :c:macro:`MPS_KEY_MAX_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted maximum size of blocks that
-      will be allocated from the pool.
+    * :c:macro:`MPS_KEY_MAX_SIZE` (type :c:type:`size_t`) is the
+      predicted maximum size of blocks that will be allocated from the
+      pool.
 
     The mean and maximum sizes are *hints* to the MPS: the pool will be
     less efficient if these are wrong, but nothing will break.
@@ -93,9 +93,9 @@ MV interface
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_mfs(),
-               (mps_arg_s[]){{MPS_KEY_MEAN_SIZE, .val.size = 32},
-                             {MPS_KEY_MAX_SIZE, .val.size = 1024},
-                             {MPS_KEY_EXTEND_BY, .val.size = 1024 * 1024},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_MEAN_SIZE, 32),
+                             MPS_ARG(MPS_KEY_MAX_SIZE, 1024),
+                             MPS_ARG(MPS_KEY_EXTEND_BY, 1024 * 1024),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/mvff.rst b/mps/manual/source/pool/mvff.rst
index df91ab9007c..bca01de026f 100644
--- a/mps/manual/source/pool/mvff.rst
+++ b/mps/manual/source/pool/mvff.rst
@@ -115,44 +115,43 @@ MVFF interface
     When creating an MVFF pool, :c:func:`mps_pool_create_k` requires
     six :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_EXTEND_BY` (member ``.val.size``; type
-      :c:type:`size_t`) is the :term:`size` of segment that the pool
-      will request from the :term:`arena`.
+    * :c:macro:`MPS_KEY_EXTEND_BY` (type :c:type:`size_t`) is the
+      :term:`size` of segment that the pool will request from the
+      :term:`arena`.
 
-    * :c:macro:`MPS_KEY_MEAN_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted mean size of blocks that will
-      be allocated from the pool. This is a *hint* to the MPS: the
-      pool will be less efficient if this is wrong, but nothing will
-      break.
+    * :c:macro:`MPS_KEY_MEAN_SIZE` (type :c:type:`size_t`) is the
+      predicted mean size of blocks that will be allocated from the
+      pool. This is a *hint* to the MPS: the pool will be less
+      efficient if this is wrong, but nothing will break.
 
-    * :c:macro:`MPS_KEY_ALIGN` (member ``.val.align``; type
-      :c:type:`mps_align_t`) is the :term:`alignment` of addresses for
-      allocation (and freeing) in the pool. If an unaligned size is
-      passed to :c:func:`mps_alloc` or :c:func:`mps_free`, it will be
-      rounded up to the pool's alignment. The minimum alignment
-      supported by pools of this class is ``sizeof(void *)``.
+    * :c:macro:`MPS_KEY_ALIGN` (type :c:type:`mps_align_t`) is the
+      :term:`alignment` of addresses for allocation (and freeing) in
+      the pool. If an unaligned size is passed to :c:func:`mps_alloc`
+      or :c:func:`mps_free`, it will be rounded up to the pool's
+      alignment. The minimum alignment supported by pools of this
+      class is ``sizeof(void *)``.
 
-    * :c:macro:`MPS_KEY_MVFF_ARENA_HIGH` (member ``.val.b``; type
-      :c:type:`mps_bool_t`) indicates whether new segments for
-      buffered allocation are acquired at high addresses (if true), or
-      at low addresses (if false).
+    * :c:macro:`MPS_KEY_MVFF_ARENA_HIGH` (type :c:type:`mps_bool_t`)
+      indicates whether new segments for buffered allocation are
+      acquired at high addresses (if true), or at low addresses (if
+      false).
 
-    * :c:macro:`MPS_KEY_MVFF_SLOT_HIGH` (member ``.val.b``; type
-      :c:type:`mps_bool_t`) is undocumented. It must have the same
-      value as :c:macro:`MPS_KEY_MVFF_ARENA_HIGH`.
+    * :c:macro:`MPS_KEY_MVFF_SLOT_HIGH` (type :c:type:`mps_bool_t`) is
+      undocumented. It must have the same value as
+      :c:macro:`MPS_KEY_MVFF_ARENA_HIGH`.
 
-    * :c:macro:`MPS_KEY_MVFF_FIRST_FIT` (member ``.val.b``; type
-      :c:type:`mps_bool_t`) is undocumented and must be set to true.
+    * :c:macro:`MPS_KEY_MVFF_FIRST_FIT` (type :c:type:`mps_bool_t`) is
+      undocumented and must be set to true.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_mvff(),
-               (mps_arg_s[]){{MPS_KEY_EXTEND_BY, .val.size = },
-                             {MPS_KEY_MEAN_SIZE, .val.size = },
-                             {MPS_KEY_ALIGN, .val.align = },
-                             {MPS_KEY_MVFF_ARENA_HIGH, .val.b = 0},
-                             {MPS_KEY_MVFF_SLOT_HIGH, .val.b = 0},
-                             {MPS_KEY_MVFF_FIRST_FIT, .val.b = 1},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_EXTEND_BY, 1024 * 1024),
+                             MPS_ARG(MPS_KEY_MEAN_SIZE, 32),
+                             MPS_ARG(MPS_KEY_ALIGN, 8),
+                             MPS_ARG(MPS_KEY_MVFF_ARENA_HIGH, 0),
+                             MPS_ARG(MPS_KEY_MVFF_SLOT_HIGH, 0),
+                             MPS_ARG(MPS_KEY_MVFF_FIRST_FIT, 1),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/mvt.rst b/mps/manual/source/pool/mvt.rst
index b670c96998e..2fa90a802c8 100644
--- a/mps/manual/source/pool/mvt.rst
+++ b/mps/manual/source/pool/mvt.rst
@@ -115,30 +115,30 @@ MVT interface
     When creating an MVT pool, :c:func:`mps_pool_create_k` requires
     five :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_MIN_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted minimum size of blocks that
-      will be allocated from the pool.
+    * :c:macro:`MPS_KEY_MIN_SIZE` (type :c:type:`size_t`) is the
+      predicted minimum size of blocks that will be allocated from the
+      pool.
 
-    * :c:macro:`MPS_KEY_MEAN_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted mean size of blocks that will
-      be allocated from the pool.
+    * :c:macro:`MPS_KEY_MEAN_SIZE` (type :c:type:`size_t`) is the
+      predicted mean size of blocks that will be allocated from the
+      pool.
 
-    * :c:macro:`MPS_KEY_MAX_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is the predicted maximum size of blocks that
-      will be allocated from the pool. Partial freeing is not
-      supported for blocks larger than this; doing so will
-      result in the storage of the block never being reused.
+    * :c:macro:`MPS_KEY_MAX_SIZE` (type :c:type:`size_t`) is the
+      predicted maximum size of blocks that will be allocated from the
+      pool. Partial freeing is not supported for blocks larger than
+      this; doing so will result in the storage of the block never
+      being reused.
 
     These three arguments are *hints* to the MPS: the pool will be
     less efficient if they are wrong, but the only thing that will
     break is the partial freeing of large blocks.
 
-    * :c:macro:`MPS_KEY_MVT_RESERVE_DEPTH` (member ``.val.count``;
-      type :c:type:`mps_count_t`) is the expected hysteresis of the
+    * :c:macro:`MPS_KEY_MVT_RESERVE_DEPTH` (type
+      :c:type:`mps_count_t`) is the expected hysteresis of the
       population of the pool. When blocks are freed, the pool will
-      retain sufficient storage to allocate this many blocks of the mean
-      size for near term allocations (rather than immediately making
-      that storage available to other pools).
+      retain sufficient storage to allocate this many blocks of the
+      mean size for near term allocations (rather than immediately
+      making that storage available to other pools).
 
       If a pool has a stable population, or one which only grows over
       the lifetime of the pool, or one which grows steadily and then
@@ -158,17 +158,16 @@ MVT interface
       object population does vary, at a slight cost in efficiency. The
       reserve does not guarantee any particular amount of allocation.
 
-    * :c:macro:`MPS_KEY_MVT_FRAG_LIMIT` (member ``.val.count``; type
-      :c:type:`mps_count_t`) is a percentage from 1 to 100
-      (inclusive). It sets an upper limit on the space overhead of an
-      MVT pool, in case block death times and allocations do not
-      correlate well. If the free space managed by the pool as a ratio
-      of all the space managed by the pool exceeds the fragmentation
-      limit, the pool falls back to a first fit allocation policy,
-      exploiting space more efficiently at a cost in time efficiency.
-      A fragmentation limit of 0 would cause the pool to operate as a
-      first-fit pool, at a significant cost in time efficiency:
-      therefore this is not permitted.
+    * :c:macro:`MPS_KEY_MVT_FRAG_LIMIT` (type :c:type:`mps_count_t`)
+      is a percentage from 1 to 100 (inclusive). It sets an upper
+      limit on the space overhead of an MVT pool, in case block death
+      times and allocations do not correlate well. If the free space
+      managed by the pool as a ratio of all the space managed by the
+      pool exceeds the fragmentation limit, the pool falls back to a
+      first fit allocation policy, exploiting space more efficiently
+      at a cost in time efficiency. A fragmentation limit of 0 would
+      cause the pool to operate as a first-fit pool, at a significant
+      cost in time efficiency: therefore this is not permitted.
 
       A fragmentation limit of 100 causes the pool to always use
       temporal fit (unless resources are exhausted). If the objects
@@ -182,11 +181,11 @@ MVT interface
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_mvt(),
-               (mps_arg_s[]){{MPS_KEY_MIN_SIZE, .val.size = 4},
-                             {MPS_KEY_MEAN_SIZE, .val.size = 32},
-                             {MPS_KEY_MAX_SIZE, .val.size = 1024},
-                             {MPS_KEY_MVT_RESERVE_DEPTH, .val.count = 256},
-                             {MPS_KEY_MVT_FRAG_LIMIT, .val.count = 50},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_MIN_SIZE, 4),
+                             MPS_ARG(MPS_KEY_MEAN_SIZE, 32),
+                             MPS_ARG(MPS_KEY_MAX_SIZE, 1024),
+                             MPS_ARG(MPS_KEY_MVT_RESERVE_DEPTH, 256),
+                             MPS_ARG(MPS_KEY_MVT_FRAG_LIMIT, 50),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/pool/snc.rst b/mps/manual/source/pool/snc.rst
index 04fd8d548ee..805beb0e892 100644
--- a/mps/manual/source/pool/snc.rst
+++ b/mps/manual/source/pool/snc.rst
@@ -98,16 +98,15 @@ SNC introspection
     When creating an SNC pool, :c:func:`mps_pool_create_k` requires one
     :term:`keyword argument`:
 
-    * :c:macro:`MPS_KEY_FORMAT` (member ``.val.format``; type
-      :c:type:`mps_fmt_t`) specifies the :term:`object format` for the
-      objects allocated in the pool. The format must provide a
-      :term:`scan method`, a :term:`skip method`, and a :term:`padding
-      method`.
+    * :c:macro:`MPS_KEY_FORMAT` (type :c:type:`mps_fmt_t`) specifies
+      the :term:`object format` for the objects allocated in the pool.
+      The format must provide a :term:`scan method`, a :term:`skip
+      method`, and a :term:`padding method`.
 
     For example, in :term:`C99`::
 
         res = mps_pool_create_k(&pool, arena, mps_class_snc(),
-               (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = fmt},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, fmt),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
@@ -122,15 +121,14 @@ SNC introspection
     When creating an :term:`allocation point` on an SNC pool,
     :c:func:`mps_ap_create_k` requires one keyword argument:
 
-    * :c:macro:`MPS_KEY_RANK` (member ``.val.rank``; type
-      :c:type:`mps_rank_t`) specifies the :term:`rank` of references
-      in objects allocated on this allocation point. It must be
-      :c:func:`mps_rank_exact`.
+    * :c:macro:`MPS_KEY_RANK` (type :c:type:`mps_rank_t`) specifies
+      the :term:`rank` of references in objects allocated on this
+      allocation point. It must be :c:func:`mps_rank_exact`.
 
     For example, in :term:`C99`::
 
         res = mps_ap_create_k(&ap, awl_pool,
-               (mps_arg_s[]){{MPS_KEY_RANK, .val.rank = mps_rank_exact()},
+               (mps_arg_s[]){MPS_ARG(MPS_KEY_RANK, mps_rank_exact()),
                              {MPS_KEY_ARGS_END}});
 
     .. deprecated:: starting with version 1.112.
diff --git a/mps/manual/source/topic/arena.rst b/mps/manual/source/topic/arena.rst
index 264ae0409b1..4dbbdcc9925 100644
--- a/mps/manual/source/topic/arena.rst
+++ b/mps/manual/source/topic/arena.rst
@@ -158,18 +158,18 @@ Client arenas
     When creating a client arena, :c:func:`mps_arena_create_k` requires two
     :term:`keyword arguments`:
 
-    * :c:macro:`MPS_KEY_ARENA_CL_ADDR` (member ``.val.addr``; type
-      :c:type:`mps_addr_t`) is the :term:`address` of the chunk of memory
-      that will be managed by the arena.
+    * :c:macro:`MPS_KEY_ARENA_CL_ADDR` (type :c:type:`mps_addr_t`) is
+      the :term:`address` of the chunk of memory that will be managed
+      by the arena.
 
-    * :c:macro:`MPS_KEY_ARENA_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`) is its size.
+    * :c:macro:`MPS_KEY_ARENA_SIZE` (type :c:type:`size_t`) is its
+      size.
 
     For example (in :term:`C99`)::
 
         res = mps_arena_create_k(&arena, mps_arena_class_cl(),
-            (mps_arg_s[]){{MPS_KEY_ARENA_CL_ADDR, .val.addr = base},
-                          {MPS_KEY_ARENA_SIZE,    .val.size = size},
+            (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_CL_ADDR, base),
+                          MPS_ARG(MPS_KEY_ARENA_SIZE, size),
                           {MPS_KEY_ARGS_END}});
 
     If the chunk is too small to hold the internal arena structures,
@@ -234,46 +234,36 @@ Virtual memory arenas
     When creating a virtual memory arena, :c:func:`mps_arena_create_k`
     requires one :term:`keyword argument`:
 
-    * :c:macro:`MPS_KEY_ARENA_SIZE` (member ``.val.size``; type
-      :c:type:`size_t`).
+    * :c:macro:`MPS_KEY_ARENA_SIZE` (type :c:type:`size_t`). is the
+      initial amount of virtual address space, in :term:`bytes (1)`,
+      that the arena will reserve (this space is initially reserved so
+      that the arena can subsequently use it without interference from
+      other parts of the program, but most of it is not committed, so
+      it doesn't require any RAM or backing store). The arena may
+      allocate more virtual address space beyond this initial
+      reservation as and when it deems it necessary. The MPS is most
+      efficient if you reserve an address space that is several times
+      larger than your peak memory usage.
 
-    For example (in :term:`C99`)::
+      .. note::
 
-        res = mps_arena_create_k(&arena, mps_arena_class_cl(),
-            (mps_arg_s[]){{MPS_KEY_ARENA_SIZE, .val.size = size},
-                          {MPS_KEY_ARGS_END}});
-
-    ``size`` is the initial amount of virtual address space, in
-    :term:`bytes (1)`, that the arena will reserve (this space is
-    initially reserved so that the arena can subsequently use it
-    without interference from other parts of the program, but most of
-    it is not committed, so it doesn't require any RAM or backing
-    store). The arena may allocate more virtual address space beyond
-    this initial reservation as and when it deems it necessary. The
-    MPS is most efficient if you reserve an address space that is
-    several times larger than your peak memory usage.
-
-    .. note::
-
-        The MPS asks for more address space if it runs out, but the
-        more times it has to extend its address space, the less
-        efficient garbage collection will become.
+          The MPS asks for more address space if it runs out, but the
+          more times it has to extend its address space, the less
+          efficient garbage collection will become.
 
     An optional :term:`keyword argument` may be passed, but is
     only used on the Windows operating system:
 
-    * :c:macro:`MPS_KEY_VMW3_TOP_DOWN` (member ``.val.b``; type
-      :c:type:`mps_bool_t`).
+    * :c:macro:`MPS_KEY_VMW3_TOP_DOWN` (type :c:type:`mps_bool_t`). If
+      true, the arena will allocate address space starting at the
+      highest possible address and working downwards through memory.
 
-    If true, the arena will allocate address space starting at the
-    highest possible address and working downwards through memory.
+      .. note::
 
-    .. note::
+          This causes the arena to pass the ``MEM_TOP_DOWN`` flag to
+          `VirtualAlloc`_.
 
-        This causes the arena to pass the ``MEM_TOP_DOWN`` flag to
-        `VirtualAlloc`_.
-
-        .. _VirtualAlloc: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366887%28v=vs.85%29.aspx
+          .. _VirtualAlloc: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366887%28v=vs.85%29.aspx
 
     If the MPS fails to reserve adequate address space to place the
     arena in, :c:func:`mps_arena_create_k` returns
@@ -285,6 +275,12 @@ Virtual memory arenas
     :c:macro:`MPS_RES_MEMORY`. Either ``size`` was far too small or
     the operating system refused to provide enough memory.
 
+    For example (in :term:`C99`)::
+
+        res = mps_arena_create_k(&arena, mps_arena_class_cl(),
+            (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_SIZE, size),
+                          {MPS_KEY_ARGS_END}});
+
     .. deprecated:: starting with version 1.112.
 
         When using :c:func:`mps_arena_create`, pass the size like
diff --git a/mps/manual/source/topic/debugging.rst b/mps/manual/source/topic/debugging.rst
index 32524d7869e..c7c372e3b2b 100644
--- a/mps/manual/source/topic/debugging.rst
+++ b/mps/manual/source/topic/debugging.rst
@@ -72,9 +72,9 @@ For example::
     mps_pool_t pool;
     mps_res_t res;
     res = mps_pool_create_k(&pool, arena, mps_class_ams_debug(),
-           (mps_arg_s[]){{MPS_KEY_POOL_DEBUG_OPTIONS, .val.pool_debug_options = &debug_options},
-                         {MPS_KEY_FORMAT, .val.format = &fmt},
-                         {MPS_KEY_CHAIN, .val.chain = &chain},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_POOL_DEBUG_OPTIONS, &debug_options),
+                         MPS_ARG(MPS_KEY_FORMAT, &fmt),
+                         MPS_ARG(MPS_KEY_CHAIN, &chain),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("can't create debug pool");
 
diff --git a/mps/manual/source/topic/format.rst b/mps/manual/source/topic/format.rst
index f3b4fd330bd..fd91f19e823 100644
--- a/mps/manual/source/topic/format.rst
+++ b/mps/manual/source/topic/format.rst
@@ -93,7 +93,7 @@ For example::
     /* obj_fmt created successfully */
 
     res = mps_pool_create_k(&obj_pool, arena, pool_class,
-           (mps_arg_s[]){{MPS_KEY_FORMAT, .val.format = obj_fmt},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_FORMAT, obj_fmt),
                          {MPS_KEY_ARGS_END}});
     if (res != MPS_RES_OK) error("Couldn't create obj pool");
 
diff --git a/mps/manual/source/topic/keyword.rst b/mps/manual/source/topic/keyword.rst
index 1acf73e34bf..74c5f17e662 100644
--- a/mps/manual/source/topic/keyword.rst
+++ b/mps/manual/source/topic/keyword.rst
@@ -30,19 +30,20 @@ For convenience and robustness, the MPS interface includes macros to
 help with forming keyword argument lists::
 
     MPS_ARGS_BEGIN(args) {
-        MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, 6553600);
-        MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, addr, base_address);
+        MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, 6553600);
+        MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, base_address);
         MPS_ARGS_DONE(args);
         res = mps_arena_create_k(&arena, mps_arena_class_cl(), args);
     } MPS_ARGS_END(args);
     
-But if you are writing :term:`C99`, you can write this more concisely as::
+But if you are writing :term:`C99`, you can write this more concisely
+using the helper macro :c:func:`MPS_ARG`::
 
     mps_res_t res;
     mps_arena_t arena;
     res = mps_arena_create_k(&arena, mps_arena_class_cl(),
-           (mps_arg_s[]){{MPS_KEY_ARENA_SIZE,    .val.size = 6553600},
-                         {MPS_KEY_ARENA_CL_ADDR, .val.addr = base_address},
+           (mps_arg_s[]){MPS_ARG(MPS_KEY_ARENA_SIZE, 6553600),
+                         MPS_ARG(MPS_KEY_ARENA_CL_ADDR, base_address),
                          {MPS_KEY_ARGS_END}});
 
 The argument array must not be ``NULL``, and must end with
@@ -87,9 +88,15 @@ now :c:macro:`MPS_KEY_ARGS_END`.
     ``key`` identifies the key. It must be one of the legal values
     of :c:type:`mps_key_t` listed in the documentation for that type.
 
-    ``val`` is the corresponding value. The documentation for each
-    value of the type :c:type:`mps_key_t` explains which structure
-    member is used by that keyword.
+    ``val`` is the corresponding value. The table given in the
+    documentation for :c:type:`mps_key_t` explains which structure
+    field is used by that keyword.
+
+    .. note::
+
+        If you use the convenience macros :c:func:`MPS_ARGS_ADD` and
+        :c:func:`MPS_ARG` you don't need to know the name of the
+        field.
 
 
 .. c:macro:: mps_args_none
@@ -106,7 +113,7 @@ now :c:macro:`MPS_KEY_ARGS_END`.
     following values:
 
     ======================================== ====================== ==========================================================
-    Keyword                                  Value slot             See
+    Keyword                                  Field                  See
     ======================================== ====================== ==========================================================
     :c:macro:`MPS_KEY_ARGS_END`              *none*                 *see above*
     :c:macro:`MPS_KEY_ALIGN`                 ``align``              :c:func:`mps_class_mvff`
@@ -138,15 +145,16 @@ now :c:macro:`MPS_KEY_ARGS_END`.
     be used like this::
 
         MPS_ARGS_BEGIN(args) {
-            MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, 6553600);
-            MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, addr, base_address);
+            MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, 6553600);
+            MPS_ARGS_ADD(args, MPS_KEY_ARENA_CL_ADDR, base_address);
             MPS_ARGS_DONE(args);
             res = mps_arena_create_k(&arena, mps_arena_class_cl(), args);
         } MPS_ARGS_END(args);
 
-    That is, you must call :c:func:`MPS_ARGS_ADD` zero or more times,
-    and then call :c:func:`MPS_ARGS_DONE` before passing the arguments
-    to a function.
+    That is, you must call :c:func:`MPS_ARGS_ADD` (or
+    :c:func:`MPS_ARGS_ADD_FIELD`) zero or more times, and then call
+    :c:func:`MPS_ARGS_DONE` before passing the arguments to a
+    function.
 
     ``args`` is the name of the array that contains the keyword
     arguments. The array is stack-allocated, and exists between
@@ -166,6 +174,35 @@ now :c:macro:`MPS_KEY_ARGS_END`.
     It must match the argument to the preceding call to
     :c:func:`MPS_ARGS_BEGIN`.
 
+    ``key`` is the keyword identifying this argument. It must be one
+    of the key names starting with ``MPS_KEY_`` that are listed in the
+    table in the documentation for :c:type:`mps_key_t`.
+
+    ``value`` is the value for this argument.
+
+
+.. c:function:: MPS_ARGS_ADD_FIELD(mps_arg_s args[], mps_key_t key, field, value)
+
+    Add an argument to a list of keyword arguments. This macro must be
+    used only between :c:macro:`MPS_ARGS_BEGIN` and
+    :c:macro:`MPS_ARGS_END`.
+
+    ``args`` is the name of array that contains the keyword arguments.
+    It must match the argument to the preceding call to
+    :c:func:`MPS_ARGS_BEGIN`.
+
+    ``key`` is the keyword identifying this argument.
+
+    ``field`` is the name of the field in the ``val`` union in the
+    structure :c:type:`mps_args_s`.
+
+    ``value`` is the value for this argument.
+
+    .. note::
+
+        You should prefer to use :c:func:`MPS_ARGS_ADD`, because then
+        you don't need to look up the name of the field.
+
 
 .. c:function:: MPS_ARGS_DONE(args)