add docstring

app.py

@@ -20,7 +20,11 @@ def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
 
 @tool
 def calculator(a: int, b: int) -> int:
-    """Multiply two integers."""
+    """Multiply two integers.
+    Args:
+        a: first integer to multiply
+        b: second integer to multiply
+    """
     return a * b