Update app.py

app.py

@@ -26,6 +26,9 @@ def countdown_tool(event_date: str, duration: int) -> str:
     Args:
         event_date (str): The event's date and time in the format "YYYY-MM-DD HH:MM".
         duration (int): A placeholder argument (not used in calculations).
+
+    Returns:
+        str: A message displaying the time remaining until the event.
     """
     try:
         event_datetime = datetime.datetime.strptime(event_date, "%Y-%m-%d %H:%M")