diff --git a/Lib/tabnanny.py b/Lib/tabnanny.py
index 2595540..5b10474 100755
--- a/Lib/tabnanny.py
+++ b/Lib/tabnanny.py
@@ -1,6 +1,16 @@
 #! /usr/bin/env python
 
-"""The Tab Nanny despises ambiguous indentation.  She knows no mercy."""
+"""The Tab Nanny despises ambiguous indentation.  She knows no mercy.
+
+tabnanny -- Detection of ambiguous indentation 
+
+For the time being this module is intended to be called as a script.
+However it is possible to import it into an IDE and use the function
+check() described below. 
+
+Warning: The API provided by this module is likely to change in future
+releases; such changes may not be backward compatible. 
+"""
 
 # Released to the public domain, by Tim Peters, 15 April 1998.
 
@@ -48,6 +58,10 @@
         check(arg)
 
 class NannyNag(Exception):
+    """
+    Raised by tokeneater() if detecting an ambiguous indent.
+    Captured and handled in check(). 
+    """
     def __init__(self, lineno, msg, line):
         self.lineno, self.msg, self.line = lineno, msg, line
     def get_lineno(self):
@@ -58,6 +72,15 @@
         return self.line
 
 def check(file):
+    """check(file_or_dir)
+    
+    If file_or_dir is a directory and not a symbolic link, then recursively
+    descend the directory tree named by file_or_dir, checking all .py files
+    along the way. If file_or_dir is an ordinary Python source file, it is
+    checked for whitespace related problems. The diagnostic messages are
+    written to standard output using the print statement.     
+    """
+    
     if os.path.isdir(file) and not os.path.islink(file):
         if verbose:
             print "%s: listing directory" % `file`