Index: trunk/Ohana/src/opihi/cmd.data/medacc.c
===================================================================
--- trunk/Ohana/src/opihi/cmd.data/medacc.c	(revision 20936)
+++ trunk/Ohana/src/opihi/cmd.data/medacc.c	(revision 42082)
@@ -10,4 +10,8 @@
   if ((argc != 6) && (argc != 7)) {
     gprint (GP_ERR, "USAGE: medacc <value> <vector> <key> start end [delta]\n");
+    gprint (GP_ERR, "  value and key are vectors of the same length\n");
+    gprint (GP_ERR, "  the output vector bins correspond to values ranging from start to end in steps of delta (default 1)\n");
+    gprint (GP_ERR, "  for a given output bin, all input values for which the key matches the output bin are averaged\n");
+
     return (FALSE);
   }