AIMessage Class — langchain Architecture

Source Code

libs/core/langchain_core/messages/ai.py lines 160–410

class AIMessage(BaseMessage):
    """Message from an AI.

    An `AIMessage` is returned from a chat model as a response to a prompt.

    This message represents the output of the model and consists of both
    the raw output as returned by the model and standardized fields
    (e.g., tool calls, usage metadata) added by the LangChain framework.
    """

    tool_calls: list[ToolCall] = Field(default_factory=list)
    """If present, tool calls associated with the message."""

    invalid_tool_calls: list[InvalidToolCall] = Field(default_factory=list)
    """If present, tool calls with parsing errors associated with the message."""

    usage_metadata: UsageMetadata | None = None
    """If present, usage metadata for a message, such as token counts.

    This is a standard representation of token usage that is consistent across models.
    """

    type: Literal["ai"] = "ai"
    """The type of the message (used for deserialization)."""

    @overload
    def __init__(
        self,
        content: str | list[str | dict],
        **kwargs: Any,
    ) -> None: ...

    @overload
    def __init__(
        self,
        content: str | list[str | dict] | None = None,
        content_blocks: list[types.ContentBlock] | None = None,
        **kwargs: Any,
    ) -> None: ...

    def __init__(
        self,
        content: str | list[str | dict] | None = None,
        content_blocks: list[types.ContentBlock] | None = None,
        **kwargs: Any,
    ) -> None:
        """Initialize an `AIMessage`.

        Specify `content` as positional arg or `content_blocks` for typing.

        Args:
            content: The content of the message.
            content_blocks: Typed standard content.
            **kwargs: Additional arguments to pass to the parent class.
        """
        if content_blocks is not None:
            # If there are tool calls in content_blocks, but not in tool_calls, add them
            content_tool_calls = [
                block for block in content_blocks if block.get("type") == "tool_call"
            ]
            if content_tool_calls and "tool_calls" not in kwargs:
                kwargs["tool_calls"] = content_tool_calls

            super().__init__(
                content=cast("str | list[str | dict]", content_blocks),
                **kwargs,
            )
        else:
            super().__init__(content=content, **kwargs)

    @property
    def lc_attributes(self) -> dict:
        """Attributes to be serialized.

        Includes all attributes, even if they are derived from other initialization
        arguments.
        """
        return {
            "tool_calls": self.tool_calls,
            "invalid_tool_calls": self.invalid_tool_calls,
        }