diff --git a/mps/code/arenacv.c b/mps/code/arenacv.c
index 18b5ba3418f..cfd124ec7d1 100644
--- a/mps/code/arenacv.c
+++ b/mps/code/arenacv.c
@@ -337,14 +337,13 @@ static void testPageTable(ArenaClass class, Size size, Addr addr)
   Arena arena; Pool pool;
   Size pageSize;
   Count tractsPerPage;
-  ArgStruct args[4];
   
-  args[0].key = MPS_KEY_ARENA_SIZE;
-  args[0].val.size = size;
-  args[1].key = MPS_KEY_ARENA_CL_ADDR;
-  args[1].val.addr = addr;
-  args[2].key = MPS_KEY_ARGS_END;
-  die(ArenaCreate(&arena, class, args), "ArenaCreate");
+  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_DONE(args);
+    die(ArenaCreate(&arena, class, args), "ArenaCreate");
+  } MPS_ARGS_END(args);
 
   die(PoolCreate(&pool, arena, PoolClassMV(), argsNone), "PoolCreate");
 
@@ -378,11 +377,11 @@ static void testSize(Size size)
   Res res;
 
   do {
-    ArgStruct args[2];
-    args[0].key = MPS_KEY_ARENA_SIZE;
-    args[0].val.size = size;
-    args[1].key = MPS_KEY_ARGS_END;
-    res = ArenaCreate(&arena, class, args);
+    MPS_ARGS_BEGIN(args) {
+      MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, size);
+      MPS_ARGS_DONE(args);
+      res = ArenaCreate(&arena, class, args);
+    } MPS_ARGS_END(args);
     if (res == ResOK)
       ArenaDestroy(arena);
     else
diff --git a/mps/code/arg.h b/mps/code/arg.h
index f50107b593f..2647937c201 100644
--- a/mps/code/arg.h
+++ b/mps/code/arg.h
@@ -37,6 +37,7 @@ extern Bool ArgCheck(Arg arg);
 extern Bool ArgListCheck(ArgList args);
 
 extern Bool ArgPick(ArgStruct *argOut, ArgList args, Key key);
+extern void ArgRequired(ArgStruct *argOut, ArgList args, Key key);
 
 extern Bool ArgCheckCant(Arg arg);
 extern Bool ArgCheckFormat(Arg arg);
@@ -49,6 +50,7 @@ extern Bool ArgCheckAlign(Arg arg);
 extern Bool ArgCheckBool(Arg arg);
 extern Bool ArgCheckCount(Arg arg);
 
+
 #endif /* arg_h */
 
 
diff --git a/mps/code/cbs.c b/mps/code/cbs.c
index 23a66699333..14e13b51b01 100644
--- a/mps/code/cbs.c
+++ b/mps/code/cbs.c
@@ -273,7 +273,6 @@ Res CBSInit(Arena arena, CBS cbs, void *owner,
             Bool mayUseInline, Bool fastFind)
 {
   Res res;
-  ArgStruct args[3];
 
   AVERT(Arena, arena);
   AVER(new == NULL || FUNCHECK(new));
@@ -287,12 +286,12 @@ Res CBSInit(Arena arena, CBS cbs, void *owner,
 
   SplayTreeInit(splayTreeOfCBS(cbs), &cbsSplayCompare,
                 fastFind ? &cbsUpdateNode : NULL);
-  args[0].key = MPS_KEY_MFS_UNIT_SIZE;
-  args[0].val.size = sizeof(CBSBlockStruct);
-  args[1].key = MPS_KEY_EXTEND_BY;
-  args[1].val.size = sizeof(CBSBlockStruct) * 64;
-  args[2].key = MPS_KEY_ARGS_END;
-  res = PoolCreate(&(cbs->blockPool), arena, PoolClassMFS(), args);
+  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_DONE(args);
+    res = PoolCreate(&(cbs->blockPool), arena, PoolClassMFS(), args);
+  } MPS_ARGS_END(args);
   if (res != ResOK)
     return res;
   cbs->splayTreeSize = 0;
diff --git a/mps/code/dbgpool.c b/mps/code/dbgpool.c
index 591a7ce39de..8d416815471 100644
--- a/mps/code/dbgpool.c
+++ b/mps/code/dbgpool.c
@@ -185,16 +185,15 @@ static Res DebugPoolInit(Pool pool, ArgList args)
   /* tag init */
   debug->tagInit = tagInit;
   if (debug->tagInit != NULL) {
-    ArgStruct pcArgs[3];
     debug->tagSize = tagSize + sizeof(tagStruct) - 1;
     /* This pool has to be like the arena control pool: the blocks */
     /* allocated must be accessible using void*. */
-    pcArgs[0].key = MPS_KEY_EXTEND_BY;
-    pcArgs[0].val.size = debug->tagSize; /* FIXME: Really? */
-    pcArgs[1].key = MPS_KEY_MFS_UNIT_SIZE;
-    pcArgs[1].val.size = debug->tagSize;
-    pcArgs[2].key = MPS_KEY_ARGS_END;
-    res = PoolCreate(&debug->tagPool, PoolArena(pool), PoolClassMFS(), pcArgs);
+    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_DONE(pcArgs);
+      res = PoolCreate(&debug->tagPool, PoolArena(pool), PoolClassMFS(), pcArgs);
+    } MPS_ARGS_END(pcArgs);
     if (res != ResOK)
       goto tagFail;
     debug->missingTags = 0;
diff --git a/mps/code/mps.h b/mps/code/mps.h
index 5f320e63c51..1a82d5c149b 100644
--- a/mps/code/mps.h
+++ b/mps/code/mps.h
@@ -119,10 +119,6 @@ extern const struct mps_key_s _mps_key_args_end;
 #define MPS_KEY_ARGS_END        (&_mps_key_args_end)
 extern mps_arg_s mps_args_none[];
 
-/* FIXME: This shouldn't be here */
-extern const struct mps_key_s _mps_key_vmw3_top_down;
-#define MPS_KEY_VMW3_TOP_DOWN   (&_mps_key_vmw3_top_down)
-
 extern const struct mps_key_s _mps_key_arena_size;
 #define MPS_KEY_ARENA_SIZE      (&_mps_key_arena_size)
 extern const struct mps_key_s _mps_key_format;
@@ -131,15 +127,44 @@ extern const struct mps_key_s _mps_key_chain;
 #define MPS_KEY_CHAIN           (&_mps_key_chain)
 
 extern const struct mps_key_s _mps_key_extend_by;
-#define MPS_KEY_EXTEND_BY (&_mps_key_extend_by)
+#define MPS_KEY_EXTEND_BY       (&_mps_key_extend_by)
 extern const struct mps_key_s _mps_key_min_size;
-#define MPS_KEY_MIN_SIZE (&_mps_key_min_size)
+#define MPS_KEY_MIN_SIZE        (&_mps_key_min_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       (&_mps_key_mean_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        (&_mps_key_max_size)
 extern const struct mps_key_s _mps_key_align;
-#define MPS_KEY_ALIGN (&_mps_key_align)
+#define MPS_KEY_ALIGN           (&_mps_key_align)
+
+/* FIXME: This will only be present on Windows. */
+extern const struct mps_key_s _mps_key_vmw3_top_down;
+#define MPS_KEY_VMW3_TOP_DOWN   (&_mps_key_vmw3_top_down)
+
+#define MPS_ARGS_BEGIN(_var) \
+  BEGIN \
+      mps_arg_s _var[ARGS_MAX]; \
+      unsigned _var##_i = 0; \
+      BEGIN
+
+#define MPS_ARGS_ADD(_var, _key, _field, _val) \
+  BEGIN \
+    /* FIXME: AVER(_var_i < ARGS_MAX); */ \
+    _var[_var##_i].key = (_key); \
+    _var[_var##_i].val._field = (_val); \
+    ++_var##_i; \
+  END
+
+#define MPS_ARGS_DONE(_var) \
+  BEGIN \
+    /* FIXME: AVER(_var##_i < ARGS_MAX); */ \
+    _var[_var##_i].key = MPS_KEY_ARGS_END; \
+    /* FIXME: _var##_i = ARGS_MAX; */ \
+  END
+
+#define MPS_ARGS_END(_var) \
+    END; \
+  END
 
 
 /* <a id="message.types"> Keep in sync with
diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index d15404aad26..8235b66c05f 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -973,18 +973,10 @@ static Res amcInitComm(Pool pool, RankSet rankSet, ArgList args)
   amc = Pool2AMC(pool);
   arena = PoolArena(pool);
 
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    pool->format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_CHAIN))
-    amc->chain = arg.val.chain;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequired(&arg, args, MPS_KEY_FORMAT);
+  pool->format = arg.val.format;
+  ArgRequired(&arg, args, MPS_KEY_CHAIN);
+  amc->chain = arg.val.chain;
   
   AVERT(Format, pool->format);
   AVERT(Chain, amc->chain);
@@ -1060,7 +1052,6 @@ failGenAlloc:
   }
   ControlFree(arena, amc->gen, genArraySize);
 failGensAlloc:
-failParam:
   return res;
 }
 
diff --git a/mps/code/poolmv.c b/mps/code/poolmv.c
index 50af068f4ed..e827e9d69b6 100644
--- a/mps/code/poolmv.c
+++ b/mps/code/poolmv.c
@@ -216,7 +216,6 @@ static Res MVInit(Pool pool, ArgList args)
   Arena arena;
   Res res;
   ArgStruct arg;
-  ArgStruct piArgs[3];
   
   if (ArgPick(&arg, args, MPS_KEY_EXTEND_BY))
     extendBy = arg.val.size;
@@ -241,23 +240,23 @@ static Res MVInit(Pool pool, ArgList args)
     blockExtendBy = sizeof(MVBlockStruct);
   }
 
-  piArgs[0].key = MPS_KEY_EXTEND_BY;
-  piArgs[0].val.size = blockExtendBy;
-  piArgs[1].key = MPS_KEY_MFS_UNIT_SIZE;
-  piArgs[1].val.size = sizeof(MVBlockStruct);
-  piArgs[2].key = MPS_KEY_ARGS_END;
-  res = PoolInit(&mv->blockPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
+  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_DONE(piArgs);
+    res = PoolInit(&mv->blockPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
+  } MPS_ARGS_END(piArgs);
   if(res != ResOK)
     return res;
 
   spanExtendBy = sizeof(MVSpanStruct) * (maxSize/extendBy);
 
-  piArgs[0].key = MPS_KEY_EXTEND_BY;
-  piArgs[0].val.size = spanExtendBy;
-  piArgs[1].key = MPS_KEY_MFS_UNIT_SIZE;
-  piArgs[1].val.size = sizeof(MVSpanStruct);
-  piArgs[2].key = MPS_KEY_ARGS_END;
-  res = PoolInit(&mv->spanPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
+  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_DONE(piArgs);
+    res = PoolInit(&mv->spanPoolStruct.poolStruct, arena, PoolClassMFS(), piArgs);
+  } MPS_ARGS_END(piArgs);
   if(res != ResOK)
     return res;
 
diff --git a/mps/code/poolncv.c b/mps/code/poolncv.c
index f7598c5539a..c250e84d2cd 100644
--- a/mps/code/poolncv.c
+++ b/mps/code/poolncv.c
@@ -32,12 +32,12 @@ static void testit(ArenaClass class, ArgList args)
 
 int main(int argc, char *argv[])
 {
-  mps_arg_s args[2];
   testlib_unused(argc);
-  args[0].key = MPS_KEY_ARENA_SIZE;
-  args[0].val.size = (Size)600000;
-  args[1].key = MPS_KEY_ARGS_END;
-  testit((ArenaClass)mps_arena_class_vm(), args);
+  MPS_ARGS_BEGIN(args) {
+    MPS_ARGS_ADD(args, MPS_KEY_ARENA_SIZE, size, 600000);
+    MPS_ARGS_DONE(args);
+    testit((ArenaClass)mps_arena_class_vm(), args);
+  } MPS_ARGS_END(args);
   printf("%s: Conclusion: Failed to find any defects.\n", argv[0]);
   return 0;
 }
diff --git a/mps/code/segsmss.c b/mps/code/segsmss.c
index 46b3e0288ee..9d69aff302a 100644
--- a/mps/code/segsmss.c
+++ b/mps/code/segsmss.c
@@ -766,18 +766,18 @@ static void *test(void *arg, size_t s)
   mps_ap_t busy_ap;
   mps_addr_t busy_init;
   char *indent = "    ";
-  mps_arg_s args[2];
 
   arena = (mps_arena_t)arg;
   (void)s; /* unused */
 
   die(mps_fmt_create_A(&format, arena, dylan_fmt_A()), "fmt_create");
 
-  args[0].key = MPS_KEY_FORMAT;
-  args[0].val.format = format;
-  args[1].key = MPS_KEY_ARGS_END;
-  die(mps_pool_create_k(&pool, arena, mps_class_amst(), args),
-      "pool_create(amst)");
+  MPS_ARGS_BEGIN(args) {
+    MPS_ARGS_ADD(args, MPS_KEY_FORMAT, format, format);
+    MPS_ARGS_DONE(args);
+    die(mps_pool_create_k(&pool, arena, mps_class_amst(), args),
+        "pool_create(amst)");
+  } MPS_ARGS_END(args);
 
   die(mps_ap_create(&ap, pool, mps_rank_exact()), "BufferCreate");
   die(mps_ap_create(&busy_ap, pool, mps_rank_exact()), "BufferCreate 2");
diff --git a/mps/manual/source/topic/interface.rst b/mps/manual/source/topic/interface.rst
index 088578f5275..fc59f4fd8f4 100644
--- a/mps/manual/source/topic/interface.rst
+++ b/mps/manual/source/topic/interface.rst
@@ -277,8 +277,18 @@ arguments are passed in a keyword argument array, like this::
     args[1].val.addr = base_address;
     args[2].key = MPS_KEY_ARGS_END;
     res = mps_arena_create_k(&arena, mps_arena_class_cl(), args);
+
+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_BASE, addr, base_address);
+      MPS_ARGS_DONE(args);
+      res = mps_arena_create_k(&arena, mps_arena_class_cl(), args);
+    } MPS_ARGS_END(args);
     
-If you are writing C99, you can write this more concisely as::
+But if you are writing C99, you can write this more concisely as::
 
     mps_res_t res;
     mps_arena_t arena;