--- a/hgext/patchbomb.py
+++ b/hgext/patchbomb.py
@@ -87,7 +87,17 @@ def diffstat(patch):
         except: pass
 
 def patchbomb(ui, repo, *revs, **opts):
-    '''send changesets as a series of patch emails'''
+    '''send changesets as a series of patch emails
+
+    The series starts with a "[PATCH 0 of N]" introduction, which
+    describes the series as a whole.
+
+    Each patch email has a Subject line of "[PATCH M of N] ...", using
+    the first line of the changeset description as the subject text.
+    The message contains two or three body parts.  First, the rest of
+    the changeset description.  Next, (optionally) if the diffstat
+    program is installed, the result of running diffstat on the patch.
+    Finally, the patch itself, as generated by "hg export".'''
     def prompt(prompt, default = None, rest = ': ', empty_ok = False):
         if default: prompt += ' [%s]' % default
         prompt += rest