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Pydantic error when using custom tool node and having runtime in the tools #1087

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opened 2026-02-20 17:43:01 -05:00 by yindo · 1 comment
yindo commented 2026-02-20 17:43:01 -05:00
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Originally created by @venki-lfc on GitHub (Dec 11, 2025).

Checked other resources

  • This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/).
  • I added a clear and detailed title that summarizes the issue.
  • I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
  • I included a self-contained, minimal example that demonstrates the issue INCLUDING all the relevant imports. The code run AS IS to reproduce the issue.

Example Code

tools_by_name = {tool.name: tool for tool in ROUTING_TOOLS}

def tool_node(state: RouterTestState):
    """Performs the tool call"""

    result = []
    for tool_call in state["router_history"][-1].tool_calls: # I access router_history instead of messages
        tool = tools_by_name[tool_call["name"]]
        observation = tool.invoke(tool_call["args"])
        result.append(ToolMessage(content=observation, tool_call_id=tool_call["id"]))
    return {"router_history": result}

#This is my tool:
@tool
def get_greeting_rules(
    runtime: ToolRuntime,
) -> Command:
    """Get guidelines for responding to greetings, small talk, and conversational queries.
    
    Call this when the user says hello, thanks you, asks about your capabilities,
    or engages in general conversation.
    """
    user_query = runtime.state.get("user_query", "")
    
    # Use LLM to generate appropriate greeting response based on rules
    llm = ChatOpenAI(**LLM_CONFIG)
    prompt = f"""{GREETING_RULES}

## User Message
{user_query}

Based on the guidelines above, give a short answer on how to respond to the user's message."""
    
    response = llm.invoke([AIMessage(content=prompt)])
    print(response)
    return Command(update={"router_history": [ToolMessage(content=response.content, tool_call_id=runtime.tool_call_id)]})

Error Message and Stack Trace (if applicable)

File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 217, in <module>
    asyncio.run(test_router())
  File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 654, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 172, in test_router
    result = await router_test_graph.ainvoke({
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\main.py", line 3158, in ainvoke
    async for chunk in self.astream(
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\main.py", line 2971, in astream
    async for _ in runner.atick(
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\_runner.py", line 304, in atick
    await arun_with_retry(
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\_retry.py", line 137, in arun_with_retry
    return await task.proc.ainvoke(task.input, config)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\_internal\_runnable.py", line 705, in ainvoke
    input = await asyncio.create_task(
            ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\_internal\_runnable.py", line 473, in ainvoke
    ret = await self.afunc(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\runnables\config.py", line 603, in run_in_executor
    return await asyncio.get_running_loop().run_in_executor(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\concurrent\futures\thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\runnables\config.py", line 594, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 48, in tool_node
    observation = tool.invoke(tool_call["args"])
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 605, in invoke
    return self.run(tool_input, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 932, in run
    raise error_to_raise
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 891, in run
    tool_args, tool_kwargs = self._to_args_and_kwargs(
                             ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 794, in _to_args_and_kwargs
    tool_input = self._parse_input(tool_input, tool_call_id)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 672, in _parse_input
    result = input_args.model_validate(tool_input)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\pydantic\main.py", line 716, in model_validate
    return cls.__pydantic_validator__.validate_python(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pydantic_core._pydantic_core.ValidationError: 1 validation error for get_greeting_rules
runtime
  Field required [type=missing, input_value={}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.12/v/missing
During task with name 'routing_tools' and id '0fc27e77-a79f-9a5d-7975-e0a92268484d'
(.venv) PS C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent>

Description

I am expecting to see this tool called without the runtime parameter. When I wrapped the tools with ToolNode from langgraph.prebuilt import ToolNode, the runtime is hidden to the LLM and there is no error. However, I get this error upon using custom tool calling node.
Could you please provide a fix?

System Info

System Information

OS: Windows
OS Version: 10.0.19045
Python Version: 3.11.9 (tags/v3.11.9:de54cf5, Apr 2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]

Package Information

langchain_core: 1.1.0
langchain: 1.1.0
langsmith: 0.4.53
langchain_openai: 1.1.0
langgraph_sdk: 0.2.12

Originally created by @venki-lfc on GitHub (Dec 11, 2025). ### Checked other resources - [x] This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/). - [x] I added a clear and detailed title that summarizes the issue. - [x] I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example). - [x] I included a self-contained, minimal example that demonstrates the issue INCLUDING all the relevant imports. The code run AS IS to reproduce the issue. ### Example Code ```python tools_by_name = {tool.name: tool for tool in ROUTING_TOOLS} def tool_node(state: RouterTestState): """Performs the tool call""" result = [] for tool_call in state["router_history"][-1].tool_calls: # I access router_history instead of messages tool = tools_by_name[tool_call["name"]] observation = tool.invoke(tool_call["args"]) result.append(ToolMessage(content=observation, tool_call_id=tool_call["id"])) return {"router_history": result} #This is my tool: @tool def get_greeting_rules( runtime: ToolRuntime, ) -> Command: """Get guidelines for responding to greetings, small talk, and conversational queries. Call this when the user says hello, thanks you, asks about your capabilities, or engages in general conversation. """ user_query = runtime.state.get("user_query", "") # Use LLM to generate appropriate greeting response based on rules llm = ChatOpenAI(**LLM_CONFIG) prompt = f"""{GREETING_RULES} ## User Message {user_query} Based on the guidelines above, give a short answer on how to respond to the user's message.""" response = llm.invoke([AIMessage(content=prompt)]) print(response) return Command(update={"router_history": [ToolMessage(content=response.content, tool_call_id=runtime.tool_call_id)]}) ``` ### Error Message and Stack Trace (if applicable) ```shell File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 217, in <module> asyncio.run(test_router()) File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 190, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 654, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 172, in test_router result = await router_test_graph.ainvoke({ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\main.py", line 3158, in ainvoke async for chunk in self.astream( File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\main.py", line 2971, in astream async for _ in runner.atick( File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\_runner.py", line 304, in atick await arun_with_retry( File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\pregel\_retry.py", line 137, in arun_with_retry return await task.proc.ainvoke(task.input, config) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\_internal\_runnable.py", line 705, in ainvoke input = await asyncio.create_task( ^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langgraph\_internal\_runnable.py", line 473, in ainvoke ret = await self.afunc(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\runnables\config.py", line 603, in run_in_executor return await asyncio.get_running_loop().run_in_executor( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\AppData\Local\Programs\Python\Python311\Lib\concurrent\futures\thread.py", line 58, in run result = self.fn(*self.args, **self.kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\runnables\config.py", line 594, in wrapper return func(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\test.py", line 48, in tool_node observation = tool.invoke(tool_call["args"]) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 605, in invoke return self.run(tool_input, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 932, in run raise error_to_raise File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 891, in run tool_args, tool_kwargs = self._to_args_and_kwargs( ^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 794, in _to_args_and_kwargs tool_input = self._parse_input(tool_input, tool_call_id) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\langchain_core\tools\base.py", line 672, in _parse_input result = input_args.model_validate(tool_input) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent\.venv\Lib\site-packages\pydantic\main.py", line 716, in model_validate return cls.__pydantic_validator__.validate_python( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pydantic_core._pydantic_core.ValidationError: 1 validation error for get_greeting_rules runtime Field required [type=missing, input_value={}, input_type=dict] For further information visit https://errors.pydantic.dev/2.12/v/missing During task with name 'routing_tools' and id '0fc27e77-a79f-9a5d-7975-e0a92268484d' (.venv) PS C:\Users\Venkatesan.KRISHNAMU\Projects\drc-agent> ``` ### Description I am expecting to see this tool called without the runtime parameter. When I wrapped the tools with ToolNode from `langgraph.prebuilt import ToolNode`, the runtime is hidden to the LLM and there is no error. However, I get this error upon using custom tool calling node. Could you please provide a fix? ### System Info System Information ------------------ > OS: Windows > OS Version: 10.0.19045 > Python Version: 3.11.9 (tags/v3.11.9:de54cf5, Apr 2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)] Package Information ------------------- > langchain_core: 1.1.0 > langchain: 1.1.0 > langsmith: 0.4.53 > langchain_openai: 1.1.0 > langgraph_sdk: 0.2.12
yindo added the bugpending labels 2026-02-20 17:43:01 -05:00
yindo closed this issue 2026-02-20 17:43:01 -05:00
yindo commented 2026-02-20 17:43:01 -05:00
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@sydney-runkle commented on GitHub (Jan 9, 2026):

Your custom tool node will need to manage the tool runtime injection. You're invoking your tool w/o the runtime, hence the error

@sydney-runkle commented on GitHub (Jan 9, 2026): Your custom tool node will need to manage the tool runtime injection. You're invoking your tool w/o the runtime, hence the error
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Reference: langchain-ai/langgraph#1087
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