added docstring tool

app.py

@@ -35,8 +35,11 @@ def get_current_time_in_timezone(timezone: str) -> str:
 
 
 @tool
-def fibonacci(n: str) -> str:
-    n = int(n)
+def fibonacci(n: int) -> str:
+    """A tool that returns Fibonacci numbers.
+    Args:
+        n: An integer indicating the nth Fibonacci number (e.g., 10).
+    """
     if n <= 0:
         return "Input should be a positive integer."
     elif n == 1: