diff --git a/docs/api.markdown b/docs/api.markdown
--- a/docs/api.markdown
+++ b/docs/api.markdown
@@ -35,9 +35,15 @@ Output format:
 
 ## Thread diff ##
 
-    /api/diff_thread/N/M/?type=O
+    /api/diff_thread
+
+Parameters:
 
-Get the diff of the thread with id=``N`` from the ``M`` timestamp in the ``O`` 
+* ``thread``: thread id
+* ``last_update``: last update timestamp
+* ``last_post``: last added post id
+
+Get the diff of the thread in the `O`` 
 format. 2 formats are available: ``html`` (used in AJAX thread update) and 
 ``json``. The default format is ``html``. Return list format: