diff --git a/SlackBot.py b/SlackBot.py
index a7bb1db..2670af1 100644
--- a/SlackBot.py
+++ b/SlackBot.py
@@ -19,6 +19,15 @@
 
 # there are no comments here
 def append_history(t):
+	"""
+	Append a session entry to the global history, keeping history length at most 20.
+	
+	Parameters:
+	    t (dict): A history entry (e.g., session data with keys like 'user' and 'time') to append.
+	
+	Returns:
+	    bool: Always returns True after appending.
+	"""
 	if len(history) > 20:
 		del history[:1]
 	history.append(t)