fix: support Callable that has __call__ as coroutine function in FunctionTool

PiperOrigin-RevId: 760913537

src/google/adk/tools/function_tool.py

@@ -33,7 +33,17 @@ class FunctionTool(BaseTool):
   """
 
   def __init__(self, func: Callable[..., Any]):
-    super().__init__(name=func.__name__, description=func.__doc__)
+    """Extract metadata from a callable object."""
+    if inspect.isfunction(func) or inspect.ismethod(func):
+      # Handle regular functions and methods
+      name = func.__name__
+      doc = func.__doc__ or ''
+    else:
+      # Handle objects with __call__ method
+      call_method = func.__call__
+      name = func.__class__.__name__
+      doc = call_method.__doc__ or func.__doc__ or ''
+    super().__init__(name=name, description=doc)
     self.func = func
 
   @override
@@ -76,7 +86,14 @@ class FunctionTool(BaseTool):
 You could retry calling this tool, but it is IMPORTANT for you to provide all the mandatory parameters."""
       return {'error': error_str}
 
-    if inspect.iscoroutinefunction(self.func):
+    # Functions are callable objects, but not all callable objects are functions
+    # checking coroutine function is not enough. We also need to check whether
+    # Callable's __call__ function is a coroutine funciton
+    if (
+        inspect.iscoroutinefunction(self.func)
+        or hasattr(self.func, '__call__')
+        and inspect.iscoroutinefunction(self.func.__call__)
+    ):
       return await self.func(**args_to_call) or {}
     else:
       return self.func(**args_to_call) or {}

tests/unittests/tools/test_function_tool.py

@@ -39,6 +39,14 @@ async def async_function_for_testing_with_2_arg_and_no_tool_context(arg1, arg2):
   return arg1
 
 
+class AsyncCallableWith2ArgsAndNoToolContext:
+
+  async def __call__(self, arg1, arg2):
+    assert arg1
+    assert arg2
+    return arg1
+
+
 def function_for_testing_with_1_arg_and_tool_context(arg1, tool_context):
   """Function for testing with 1 arge and tool context."""
   assert arg1
@@ -46,6 +54,14 @@ def function_for_testing_with_1_arg_and_tool_context(arg1, tool_context):
   return arg1
 
 
+class AsyncCallableWith1ArgAndToolContext:
+
+  async def __call__(self, arg1, tool_context):
+    assert arg1
+    assert tool_context
+    return arg1
+
+
 def function_for_testing_with_2_arg_and_no_tool_context(arg1, arg2):
   """Function for testing with 2 arge and no tool context."""
   assert arg1
@@ -83,6 +99,16 @@ async def test_run_async_with_tool_context_async_func():
   assert result == "test_value_1"
 
 
+@pytest.mark.asyncio
+async def test_run_async_with_tool_context_async_callable():
+  """Test that run_async calls the callable with tool_context when tool_context is in signature (async callable)."""
+
+  tool = FunctionTool(AsyncCallableWith1ArgAndToolContext())
+  args = {"arg1": "test_value_1"}
+  result = await tool.run_async(args=args, tool_context=MagicMock())
+  assert result == "test_value_1"
+
+
 @pytest.mark.asyncio
 async def test_run_async_without_tool_context_async_func():
   """Test that run_async calls the function without tool_context when tool_context is not in signature (async function)."""
@@ -92,6 +118,15 @@ async def test_run_async_without_tool_context_async_func():
   assert result == "test_value_1"
 
 
+@pytest.mark.asyncio
+async def test_run_async_without_tool_context_async_callable():
+  """Test that run_async calls the callable without tool_context when tool_context is not in signature (async callable)."""
+  tool = FunctionTool(AsyncCallableWith2ArgsAndNoToolContext())
+  args = {"arg1": "test_value_1", "arg2": "test_value_2"}
+  result = await tool.run_async(args=args, tool_context=MagicMock())
+  assert result == "test_value_1"
+
+
 @pytest.mark.asyncio
 async def test_run_async_with_tool_context_sync_func():
   """Test that run_async calls the function with tool_context when tool_context is in signature (synchronous function)."""