tool.py — langchain Source File

Source Code

"""Messages for tools."""

import json
from typing import Any, Literal, cast, overload
from uuid import UUID

from pydantic import Field, model_validator
from typing_extensions import NotRequired, TypedDict, override

from langchain_core.messages import content as types
from langchain_core.messages.base import BaseMessage, BaseMessageChunk, merge_content
from langchain_core.messages.content import InvalidToolCall
from langchain_core.utils._merge import merge_dicts, merge_obj


class ToolOutputMixin:
    """Mixin for objects that tools can return directly.

    If a custom BaseTool is invoked with a `ToolCall` and the output of custom code is
    not an instance of `ToolOutputMixin`, the output will automatically be coerced to
    a string and wrapped in a `ToolMessage`.

    """


class ToolMessage(BaseMessage, ToolOutputMixin):
    """Message for passing the result of executing a tool back to a model.

    `ToolMessage` objects contain the result of a tool invocation. Typically, the result
    is encoded inside the `content` field.

    `tool_call_id` is used to associate the tool call request with the tool call
    response. Useful in situations where a chat model is able to request multiple tool
    calls in parallel.

    Example:
        A `ToolMessage` representing a result of `42` from a tool call with id

        ```python
        from langchain_core.messages import ToolMessage

        ToolMessage(content="42", tool_call_id="call_Jja7J89XsjrOLA5r!MEOW!SL")
        ```

    Example:
        A `ToolMessage` where only part of the tool output is sent to the model
        and the full output is passed in to artifact.

        ```python
        from langchain_core.messages import ToolMessage

        tool_output = {
            "stdout": "From the graph we can see that the correlation between "
            "x and y is ...",
            "stderr": None,
            "artifacts": {"type": "image", "base64_data": "/9j/4gIcSU..."},
        }

        ToolMessage(
            content=tool_output["stdout"],
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