feat:support Langchain tools that has run_manager in _run args and don't have args_schema populated

PiperOrigin-RevId: 765405793

contributing/samples/langchain_youtube_search_agent/README.md

@@ -0,0 +1,8 @@
+# Langchain Youtube Search Agent
+
+This agent utilize the Lanchain YoutubeSearchTool to search youtubes.
+You need to install below dependencies:
+
+```python
+uv pip install youtube_search
+``` 

contributing/samples/langchain_youtube_search_agent/__init__.py

@@ -0,0 +1,15 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from . import agent

contributing/samples/langchain_youtube_search_agent/agent.py

@@ -0,0 +1,36 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from google.adk.agents import LlmAgent
+from google.adk.tools.langchain_tool import LangchainTool
+from langchain_community.tools import YouTubeSearchTool
+
+# Instantiate the tool
+langchain_yt_tool = YouTubeSearchTool()
+
+# Wrap the tool in the LangchainTool class from ADK
+adk_yt_tool = LangchainTool(
+    tool=langchain_yt_tool,
+)
+
+root_agent = LlmAgent(
+    name="youtube_search_agent",
+    model="gemini-2.0-flash",  # Replace with the actual model name
+    instruction="""
+    Ask customer to provide singer name, and the number of videos to search.
+    """,
+    description="Help customer to search for a video on Youtube.",
+    tools=[adk_yt_tool],
+    output_key="youtube_search_output",
+)

src/google/adk/tools/langchain_tool.py

@@ -70,7 +70,8 @@ class LangchainTool(FunctionTool):
     else:
       func = tool._run if hasattr(tool, '_run') else tool.run
     super().__init__(func)
-
+    # run_manager is a special parameter for langchain tool
+    self._ignore_params.append('run_manager')
     self._langchain_tool = tool
 
     # Set name: priority is 1) explicitly provided name, 2) tool's name, 3) default
@@ -122,15 +123,16 @@ class LangchainTool(FunctionTool):
               self.name,
               self.description,
               tool_wrapper.func,
-            getattr(tool_wrapper, 'args', None),
+              tool_wrapper.args,
           )
 
       # Need to provide a way to override the function names and descriptions
       # as the original function names are mostly ".run" and the descriptions
       # may not meet users' needs
-      return _automatic_function_calling_util.build_function_declaration(
+      function_decl = super()._get_declaration()
-          func=self._langchain_tool.run,
+      function_decl.name = self.name
-      )
+      function_decl.description = self.description
+      return function_decl
 
     except Exception as e:
       raise ValueError(