I have adapted this notebook from various tutorials:

https://colab.research.google.com/drive/1tAa5QUWplKRbYsUROZ1tmPiEZ4kY9sio?usp=sharing

I want to make this model into a tool and call the tool to parse human input as a node in langgraph:

class PlanItem(BaseModel):
    step: str
    tools: Optional[str] = []
    data_sources: Optional[str] = []
    sub_steps_needed: str

class Plan(BaseModel):
    plan: List[PlanItem] 

This function should create the agent for the node:

def create_agent(llm: ChatOpenAI, tools: list, system_prompt: str):
    # Each worker node will be given a name and some tools.
    prompt = ChatPromptTemplate.from_messages(
        [
            (
                "system",
                system_prompt,
            ),
            MessagesPlaceholder(variable_name="messages"),
            MessagesPlaceholder(variable_name="agent_scratchpad"),
        ]
    )
    agent = create_openai_tools_agent(llm, tools, prompt)
    executor = AgentExecutor(agent=agent, tools=tools)
    return executor

but it doesn’t recognise Plan as a BaseModel and I cannot convert it to a function I can pass as a tool.

Using pydantic.v1 I tried several approaches using PydanticOutputParser, PydanticOutputFunctionsParser and PydanticToolsParser. I also tried using convert_pydantic_to_openai_function:

output_parser = PydanticOutputParser(pydantic_object=Plan)

output_parser = PydanticOutputFunctionsParser(pydantic_schema=Plan)

output_parser = PydanticToolsParser(tools=[Plan])

output_parser = convert_pydantic_to_openai_function(Plan) output_parser['description'] = "Parses data into Plan" output_parser['title'] = "Plan Parser"

I seem to get errors which are variations on:

ValueError: Unsupported function

pydantic_schema=<class '__main__.Plan'>

Functions must be passed in as Dict, pydantic.BaseModel, or Callable. If they're a dict they must either be in OpenAI function format or valid JSON schema with top-level 'title' and 'description' keys.

There are tutorials on generally adding the parser as a tool in langchain, but I want the parser to only be invoked at a particular node.

Can anybody show me how to do this?