langchain-ai/langchain · error · ValueError

Tool/function already has a 'strict' key with value {oai_fun

Error message

Tool/function already has a 'strict' key with value {oai_function['strict']} which is different from the explicit `strict` arg received {strict=}.

What it means

Error "Tool/function already has a 'strict' key with value {oai_function['strict']} which is different from the explicit `strict` arg received {strict=}." thrown in langchain-ai/langchain.

Source

Thrown at libs/core/langchain_core/utils/function_calling.py:477

                "function name."
            )
            raise ValueError(msg)
        msg = (
            f"Unsupported function\n\n{function}\n\nFunctions 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' key."
        )
        raise ValueError(msg)

    if strict is not None:
        if "strict" in oai_function and oai_function["strict"] != strict:
            msg = (
                f"Tool/function already has a 'strict' key with value "
                f"{oai_function['strict']} which is different from the explicit "
                f"`strict` arg received {strict=}."
            )
            raise ValueError(msg)
        oai_function["strict"] = strict
        if strict:
            # All fields must be `required`
            parameters = oai_function.get("parameters")
            if isinstance(parameters, dict):
                fields = parameters.get("properties")
                if isinstance(fields, dict) and fields:
                    parameters = dict(parameters)
                    parameters["required"] = list(fields.keys())
                    oai_function["parameters"] = parameters

            # As of 08/06/24, OpenAI requires that additionalProperties be supplied and
            # set to False if strict is True.
            # All properties layer needs 'additionalProperties=False'
            oai_function["parameters"] = _recursive_set_additional_properties_false(
                oai_function["parameters"]
            )
    return oai_function

View on GitHub (pinned to e32fa9a52e)

Solutions

1. Set 'strict' in exactly one place: either inside the function dict or via the explicit strict argument, not both with different values.
2. Make the two values agree, or drop the embedded 'strict' key and use the strict= keyword.

Example fix

convert_to_openai_tool(schema, strict=True)  # remove 'strict' from schema dict

When it happens

Trigger: Raised when the function dict already contains a 'strict' key and an explicit strict argument with a conflicting value is also passed.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langchain@e32fa9a52e (2026-08-14). Data as JSON: /api/errors/420c017939a4f23e. Report an issue: GitHub.