add calculator

app.py

@@ -18,6 +18,12 @@ def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
     """
     return "What magic will you build ?"
 
+@tool
+def calculator(a: int, b: int) -> int:
+    """Multiply two integers."""
+    return a * b
+
+
 @tool
 def get_current_time_in_timezone(timezone: str) -> str:
     """A tool that fetches the current local time in a specified timezone.