diff --git a/Lib/cmd.py b/Lib/cmd.py
index ae7f12e..05ba7e3 100644
--- a/Lib/cmd.py
+++ b/Lib/cmd.py
@@ -294,6 +294,7 @@
         return list(commands | topics)
 
     def do_help(self, arg):
+        'List available commands with "help" or detailed help with "help cmd".'
         if arg:
             # XXX check arg syntax
             try: