langchain/libs/core/langchain_core/tools.py

"""Base implementation for tools or skills."""
from __future__ import annotations

import inspect
import warnings
from abc import abstractmethod
from inspect import signature
from typing import Any, Awaitable, Callable, Dict, List, Optional, Tuple, Type, Union

from langchain_core.callbacks import (
    AsyncCallbackManager,
    AsyncCallbackManagerForToolRun,
    BaseCallbackManager,
    CallbackManager,
    CallbackManagerForToolRun,
    Callbacks,
)
from langchain_core.load.serializable import Serializable
from langchain_core.pydantic_v1 import (
    BaseModel,
    Extra,
    Field,
    create_model,
    root_validator,
    validate_arguments,
)
from langchain_core.runnables import (
    Runnable,
    RunnableConfig,
    RunnableSerializable,
    ensure_config,
)
from langchain_core.runnables.config import run_in_executor


class SchemaAnnotationError(TypeError):
    """Raised when 'args_schema' is missing or has an incorrect type annotation."""


def _create_subset_model(
    name: str, model: BaseModel, field_names: list
) -> Type[BaseModel]:
    """Create a pydantic model with only a subset of model's fields."""
    fields = {}
    for field_name in field_names:
        field = model.__fields__[field_name]
        fields[field_name] = (field.outer_type_, field.field_info)
    return create_model(name, **fields)  # type: ignore


def _get_filtered_args(
    inferred_model: Type[BaseModel],
    func: Callable,
) -> dict:
    """Get the arguments from a function's signature."""
    schema = inferred_model.schema()["properties"]
    valid_keys = signature(func).parameters
    return {k: schema[k] for k in valid_keys if k not in ("run_manager", "callbacks")}


class _SchemaConfig:
    """Configuration for the pydantic model."""

    extra: Any = Extra.forbid
    arbitrary_types_allowed: bool = True


def create_schema_from_function(
    model_name: str,
    func: Callable,
) -> Type[BaseModel]:
    """Create a pydantic schema from a function's signature.
    Args:
        model_name: Name to assign to the generated pydandic schema
        func: Function to generate the schema from
    Returns:
        A pydantic model with the same arguments as the function
    """
    # https://docs.pydantic.dev/latest/usage/validation_decorator/
    validated = validate_arguments(func, config=_SchemaConfig)  # type: ignore
    inferred_model = validated.model  # type: ignore
    if "run_manager" in inferred_model.__fields__:
        del inferred_model.__fields__["run_manager"]
    if "callbacks" in inferred_model.__fields__:
        del inferred_model.__fields__["callbacks"]
    # Pydantic adds placeholder virtual fields we need to strip
    valid_properties = _get_filtered_args(inferred_model, func)
    return _create_subset_model(
        f"{model_name}Schema", inferred_model, list(valid_properties)
    )


class ToolException(Exception):
    """An optional exception that tool throws when execution error occurs.

    When this exception is thrown, the agent will not stop working,
    but will handle the exception according to the handle_tool_error
    variable of the tool, and the processing result will be returned
    to the agent as observation, and printed in red on the console.
    """

    pass


class BaseTool(RunnableSerializable[Union[str, Dict], Any]):
    """Interface LangChain tools must implement."""

    def __init_subclass__(cls, **kwargs: Any) -> None:
        """Create the definition of the new tool class."""
        super().__init_subclass__(**kwargs)

        args_schema_type = cls.__annotations__.get("args_schema", None)

        if args_schema_type is not None:
            if args_schema_type is None or args_schema_type == BaseModel:
                # Throw errors for common mis-annotations.
                # TODO: Use get_args / get_origin and fully
                # specify valid annotations.
                typehint_mandate = """
class ChildTool(BaseTool):
    ...
    args_schema: Type[BaseModel] = SchemaClass
    ..."""
                name = cls.__name__
                raise SchemaAnnotationError(
                    f"Tool definition for {name} must include valid type annotations"
                    f" for argument 'args_schema' to behave as expected.\n"
                    f"Expected annotation of 'Type[BaseModel]'"
                    f" but got '{args_schema_type}'.\n"
                    f"Expected class looks like:\n"
                    f"{typehint_mandate}"
                )

    name: str
    """The unique name of the tool that clearly communicates its purpose."""
    description: str
    """Used to tell the model how/when/why to use the tool.
    
    You can provide few-shot examples as a part of the description.
    """
    args_schema: Optional[Type[BaseModel]] = None
    """Pydantic model class to validate and parse the tool's input arguments."""
    return_direct: bool = False
    """Whether to return the tool's output directly. Setting this to True means
    
    that after the tool is called, the AgentExecutor will stop looping.
    """
    verbose: bool = False
    """Whether to log the tool's progress."""

    callbacks: Callbacks = Field(default=None, exclude=True)
    """Callbacks to be called during tool execution."""
    callback_manager: Optional[BaseCallbackManager] = Field(default=None, exclude=True)
    """Deprecated. Please use callbacks instead."""
    tags: Optional[List[str]] = None
    """Optional list of tags associated with the tool. Defaults to None
    These tags will be associated with each call to this tool,
    and passed as arguments to the handlers defined in `callbacks`.
    You can use these to eg identify a specific instance of a tool with its use case.
    """
    metadata: Optional[Dict[str, Any]] = None
    """Optional metadata associated with the tool. Defaults to None
    This metadata will be associated with each call to this tool,
    and passed as arguments to the handlers defined in `callbacks`.
    You can use these to eg identify a specific instance of a tool with its use case.
    """

    handle_tool_error: Optional[
        Union[bool, str, Callable[[ToolException], str]]
    ] = False
    """Handle the content of the ToolException thrown."""

    class Config(Serializable.Config):
        """Configuration for this pydantic object."""

        arbitrary_types_allowed = True

    @property
    def is_single_input(self) -> bool:
        """Whether the tool only accepts a single input."""
        keys = {k for k in self.args if k != "kwargs"}
        return len(keys) == 1

    @property
    def args(self) -> dict:
        if self.args_schema is not None:
            return self.args_schema.schema()["properties"]
        else:
            schema = create_schema_from_function(self.name, self._run)
            return schema.schema()["properties"]

    # --- Runnable ---

    def get_input_schema(
        self, config: Optional[RunnableConfig] = None
    ) -> Type[BaseModel]:
        """The tool's input schema."""
        if self.args_schema is not None:
            return self.args_schema
        else:
            return create_schema_from_function(self.name, self._run)

    def invoke(
        self,
        input: Union[str, Dict],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> Any:
        config = ensure_config(config)
        return self.run(
            input,
            callbacks=config.get("callbacks"),
            tags=config.get("tags"),
            metadata=config.get("metadata"),
            run_name=config.get("run_name"),
            **kwargs,
        )

    async def ainvoke(
        self,
        input: Union[str, Dict],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> Any:
        config = ensure_config(config)
        return await self.arun(
            input,
            callbacks=config.get("callbacks"),
            tags=config.get("tags"),
            metadata=config.get("metadata"),
            run_name=config.get("run_name"),
            **kwargs,
        )

    # --- Tool ---

    def _parse_input(
        self,
        tool_input: Union[str, Dict],
    ) -> Union[str, Dict[str, Any]]:
        """Convert tool input to pydantic model."""
        input_args = self.args_schema
        if isinstance(tool_input, str):
            if input_args is not None:
                key_ = next(iter(input_args.__fields__.keys()))
                input_args.validate({key_: tool_input})
            return tool_input
        else:
            if input_args is not None:
                result = input_args.parse_obj(tool_input)
                return {k: v for k, v in result.dict().items() if k in tool_input}
        return tool_input

    @root_validator()
    def raise_deprecation(cls, values: Dict) -> Dict:
        """Raise deprecation warning if callback_manager is used."""
        if values.get("callback_manager") is not None:
            warnings.warn(
                "callback_manager is deprecated. Please use callbacks instead.",
                DeprecationWarning,
            )
            values["callbacks"] = values.pop("callback_manager", None)
        return values

    @abstractmethod
    def _run(
        self,
        *args: Any,
        **kwargs: Any,
    ) -> Any:
        """Use the tool.

        Add run_manager: Optional[CallbackManagerForToolRun] = None
        to child implementations to enable tracing,
        """

    async def _arun(
        self,
        *args: Any,
        **kwargs: Any,
    ) -> Any:
        """Use the tool asynchronously.

        Add run_manager: Optional[AsyncCallbackManagerForToolRun] = None
        to child implementations to enable tracing,
        """
        return await run_in_executor(None, self._run, *args, **kwargs)

    def _to_args_and_kwargs(self, tool_input: Union[str, Dict]) -> Tuple[Tuple, Dict]:
        # For backwards compatibility, if run_input is a string,
        # pass as a positional argument.
        if isinstance(tool_input, str):
            return (tool_input,), {}
        else:
            return (), tool_input

    def run(
        self,
        tool_input: Union[str, Dict],
        verbose: Optional[bool] = None,
        start_color: Optional[str] = "green",
        color: Optional[str] = "green",
        callbacks: Callbacks = None,
        *,
        tags: Optional[List[str]] = None,
        metadata: Optional[Dict[str, Any]] = None,
        run_name: Optional[str] = None,
        **kwargs: Any,
    ) -> Any:
        """Run the tool."""
        parsed_input = self._parse_input(tool_input)
        if not self.verbose and verbose is not None:
            verbose_ = verbose
        else:
            verbose_ = self.verbose
        callback_manager = CallbackManager.configure(
            callbacks,
            self.callbacks,
            verbose_,
            tags,
            self.tags,
            metadata,
            self.metadata,
        )
        # TODO: maybe also pass through run_manager is _run supports kwargs
        new_arg_supported = signature(self._run).parameters.get("run_manager")
        run_manager = callback_manager.on_tool_start(
            {"name": self.name, "description": self.description},
            tool_input if isinstance(tool_input, str) else str(tool_input),
            color=start_color,
            name=run_name,
            **kwargs,
        )
        try:
            tool_args, tool_kwargs = self._to_args_and_kwargs(parsed_input)
            observation = (
                self._run(*tool_args, run_manager=run_manager, **tool_kwargs)
                if new_arg_supported
                else self._run(*tool_args, **tool_kwargs)
            )
        except ToolException as e:
            if not self.handle_tool_error:
                run_manager.on_tool_error(e)
                raise e
            elif isinstance(self.handle_tool_error, bool):
                if e.args:
                    observation = e.args[0]
                else:
                    observation = "Tool execution error"
            elif isinstance(self.handle_tool_error, str):
                observation = self.handle_tool_error
            elif callable(self.handle_tool_error):
                observation = self.handle_tool_error(e)
            else:
                raise ValueError(
                    f"Got unexpected type of `handle_tool_error`. Expected bool, str "
                    f"or callable. Received: {self.handle_tool_error}"
                )
            run_manager.on_tool_end(
                str(observation), color="red", name=self.name, **kwargs
            )
            return observation
        except (Exception, KeyboardInterrupt) as e:
            run_manager.on_tool_error(e)
            raise e
        else:
            run_manager.on_tool_end(
                str(observation), color=color, name=self.name, **kwargs
            )
            return observation

    async def arun(
        self,
        tool_input: Union[str, Dict],
        verbose: Optional[bool] = None,
        start_color: Optional[str] = "green",
        color: Optional[str] = "green",
        callbacks: Callbacks = None,
        *,
        tags: Optional[List[str]] = None,
        metadata: Optional[Dict[str, Any]] = None,
        run_name: Optional[str] = None,
        **kwargs: Any,
    ) -> Any:
        """Run the tool asynchronously."""
        parsed_input = self._parse_input(tool_input)
        if not self.verbose and verbose is not None:
            verbose_ = verbose
        else:
            verbose_ = self.verbose
        callback_manager = AsyncCallbackManager.configure(
            callbacks,
            self.callbacks,
            verbose_,
            tags,
            self.tags,
            metadata,
            self.metadata,
        )
        new_arg_supported = signature(self._arun).parameters.get("run_manager")
        run_manager = await callback_manager.on_tool_start(
            {"name": self.name, "description": self.description},
            tool_input if isinstance(tool_input, str) else str(tool_input),
            color=start_color,
            name=run_name,
            **kwargs,
        )
        try:
            # We then call the tool on the tool input to get an observation
            tool_args, tool_kwargs = self._to_args_and_kwargs(parsed_input)
            observation = (
                await self._arun(*tool_args, run_manager=run_manager, **tool_kwargs)
                if new_arg_supported
                else await self._arun(*tool_args, **tool_kwargs)
            )
        except ToolException as e:
            if not self.handle_tool_error:
                await run_manager.on_tool_error(e)
                raise e
            elif isinstance(self.handle_tool_error, bool):
                if e.args:
                    observation = e.args[0]
                else:
                    observation = "Tool execution error"
            elif isinstance(self.handle_tool_error, str):
                observation = self.handle_tool_error
            elif callable(self.handle_tool_error):
                observation = self.handle_tool_error(e)
            else:
                raise ValueError(
                    f"Got unexpected type of `handle_tool_error`. Expected bool, str "
                    f"or callable. Received: {self.handle_tool_error}"
                )
            await run_manager.on_tool_end(
                str(observation), color="red", name=self.name, **kwargs
            )
            return observation
        except (Exception, KeyboardInterrupt) as e:
            await run_manager.on_tool_error(e)
            raise e
        else:
            await run_manager.on_tool_end(
                str(observation), color=color, name=self.name, **kwargs
            )
            return observation

    def __call__(self, tool_input: str, callbacks: Callbacks = None) -> str:
        """Make tool callable."""
        return self.run(tool_input, callbacks=callbacks)


class Tool(BaseTool):
    """Tool that takes in function or coroutine directly."""

    description: str = ""
    func: Optional[Callable[..., str]]
    """The function to run when the tool is called."""
    coroutine: Optional[Callable[..., Awaitable[str]]] = None
    """The asynchronous version of the function."""

    # --- Runnable ---

    async def ainvoke(
        self,
        input: Union[str, Dict],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> Any:
        if not self.coroutine:
            # If the tool does not implement async, fall back to default implementation
            return await run_in_executor(config, self.invoke, input, config, **kwargs)

        return await super().ainvoke(input, config, **kwargs)

    # --- Tool ---

    @property
    def args(self) -> dict:
        """The tool's input arguments."""
        if self.args_schema is not None:
            return self.args_schema.schema()["properties"]
        # For backwards compatibility, if the function signature is ambiguous,
        # assume it takes a single string input.
        return {"tool_input": {"type": "string"}}

    def _to_args_and_kwargs(self, tool_input: Union[str, Dict]) -> Tuple[Tuple, Dict]:
        """Convert tool input to pydantic model."""
        args, kwargs = super()._to_args_and_kwargs(tool_input)
        # For backwards compatibility. The tool must be run with a single input
        all_args = list(args) + list(kwargs.values())
        if len(all_args) != 1:
            raise ToolException(
                f"Too many arguments to single-input tool {self.name}."
                f" Args: {all_args}"
            )
        return tuple(all_args), {}

    def _run(
        self,
        *args: Any,
        run_manager: Optional[CallbackManagerForToolRun] = None,
        **kwargs: Any,
    ) -> Any:
        """Use the tool."""
        if self.func:
            new_argument_supported = signature(self.func).parameters.get("callbacks")
            return (
                self.func(
                    *args,
                    callbacks=run_manager.get_child() if run_manager else None,
                    **kwargs,
                )
                if new_argument_supported
                else self.func(*args, **kwargs)
            )
        raise NotImplementedError("Tool does not support sync")

    async def _arun(
        self,
        *args: Any,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
        **kwargs: Any,
    ) -> Any:
        """Use the tool asynchronously."""
        if self.coroutine:
            new_argument_supported = signature(self.coroutine).parameters.get(
                "callbacks"
            )
            return (
                await self.coroutine(
                    *args,
                    callbacks=run_manager.get_child() if run_manager else None,
                    **kwargs,
                )
                if new_argument_supported
                else await self.coroutine(*args, **kwargs)
            )
        else:
            return await run_in_executor(
                None,
                self._run,
                run_manager=run_manager.get_sync() if run_manager else None,
                *args,
                **kwargs,
            )

    # TODO: this is for backwards compatibility, remove in future
    def __init__(
        self, name: str, func: Optional[Callable], description: str, **kwargs: Any
    ) -> None:
        """Initialize tool."""
        super(Tool, self).__init__(
            name=name, func=func, description=description, **kwargs
        )

    @classmethod
    def from_function(
        cls,
        func: Optional[Callable],
        name: str,  # We keep these required to support backwards compatibility
        description: str,
        return_direct: bool = False,
        args_schema: Optional[Type[BaseModel]] = None,
        coroutine: Optional[
            Callable[..., Awaitable[Any]]
        ] = None,  # This is last for compatibility, but should be after func
        **kwargs: Any,
    ) -> Tool:
        """Initialize tool from a function."""
        if func is None and coroutine is None:
            raise ValueError("Function and/or coroutine must be provided")
        return cls(
            name=name,
            func=func,
            coroutine=coroutine,
            description=description,
            return_direct=return_direct,
            args_schema=args_schema,
            **kwargs,
        )


class StructuredTool(BaseTool):
    """Tool that can operate on any number of inputs."""

    description: str = ""
    args_schema: Type[BaseModel] = Field(..., description="The tool schema.")
    """The input arguments' schema."""
    func: Optional[Callable[..., Any]]
    """The function to run when the tool is called."""
    coroutine: Optional[Callable[..., Awaitable[Any]]] = None
    """The asynchronous version of the function."""

    # --- Runnable ---

    async def ainvoke(
        self,
        input: Union[str, Dict],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> Any:
        if not self.coroutine:
            # If the tool does not implement async, fall back to default implementation
            return await run_in_executor(config, self.invoke, input, config, **kwargs)

        return await super().ainvoke(input, config, **kwargs)

    # --- Tool ---

    @property
    def args(self) -> dict:
        """The tool's input arguments."""
        return self.args_schema.schema()["properties"]

    def _run(
        self,
        *args: Any,
        run_manager: Optional[CallbackManagerForToolRun] = None,
        **kwargs: Any,
    ) -> Any:
        """Use the tool."""
        if self.func:
            new_argument_supported = signature(self.func).parameters.get("callbacks")
            return (
                self.func(
                    *args,
                    callbacks=run_manager.get_child() if run_manager else None,
                    **kwargs,
                )
                if new_argument_supported
                else self.func(*args, **kwargs)
            )
        raise NotImplementedError("Tool does not support sync")

    async def _arun(
        self,
        *args: Any,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
        **kwargs: Any,
    ) -> str:
        """Use the tool asynchronously."""
        if self.coroutine:
            new_argument_supported = signature(self.coroutine).parameters.get(
                "callbacks"
            )
            return (
                await self.coroutine(
                    *args,
                    callbacks=run_manager.get_child() if run_manager else None,
                    **kwargs,
                )
                if new_argument_supported
                else await self.coroutine(*args, **kwargs)
            )
        return await run_in_executor(
            None,
            self._run,
            run_manager=run_manager.get_sync() if run_manager else None,
            *args,
            **kwargs,
        )

    @classmethod
    def from_function(
        cls,
        func: Optional[Callable] = None,
        coroutine: Optional[Callable[..., Awaitable[Any]]] = None,
        name: Optional[str] = None,
        description: Optional[str] = None,
        return_direct: bool = False,
        args_schema: Optional[Type[BaseModel]] = None,
        infer_schema: bool = True,
        **kwargs: Any,
    ) -> StructuredTool:
        """Create tool from a given function.

        A classmethod that helps to create a tool from a function.

        Args:
            func: The function from which to create a tool
            coroutine: The async function from which to create a tool
            name: The name of the tool. Defaults to the function name
            description: The description of the tool. Defaults to the function docstring
            return_direct: Whether to return the result directly or as a callback
            args_schema: The schema of the tool's input arguments
            infer_schema: Whether to infer the schema from the function's signature
            **kwargs: Additional arguments to pass to the tool

        Returns:
            The tool

        Examples:

            .. code-block:: python

                def add(a: int, b: int) -> int:
                    \"\"\"Add two numbers\"\"\"
                    return a + b
                tool = StructuredTool.from_function(add)
                tool.run(1, 2) # 3
        """

        if func is not None:
            source_function = func
        elif coroutine is not None:
            source_function = coroutine
        else:
            raise ValueError("Function and/or coroutine must be provided")
        name = name or source_function.__name__
        description = description or source_function.__doc__
        if description is None:
            raise ValueError(
                "Function must have a docstring if description not provided."
            )

        # Description example:
        # search_api(query: str) - Searches the API for the query.
        sig = signature(source_function)
        description = f"{name}{sig} - {description.strip()}"
        _args_schema = args_schema
        if _args_schema is None and infer_schema:
            _args_schema = create_schema_from_function(f"{name}Schema", source_function)
        return cls(
            name=name,
            func=func,
            coroutine=coroutine,
            args_schema=_args_schema,
            description=description,
            return_direct=return_direct,
            **kwargs,
        )


def tool(
    *args: Union[str, Callable, Runnable],
    return_direct: bool = False,
    args_schema: Optional[Type[BaseModel]] = None,
    infer_schema: bool = True,
) -> Callable:
    """Make tools out of functions, can be used with or without arguments.

    Args:
        *args: The arguments to the tool.
        return_direct: Whether to return directly from the tool rather
            than continuing the agent loop.
        args_schema: optional argument schema for user to specify
        infer_schema: Whether to infer the schema of the arguments from
            the function's signature. This also makes the resultant tool
            accept a dictionary input to its `run()` function.

    Requires:
        - Function must be of type (str) -> str
        - Function must have a docstring

    Examples:
        .. code-block:: python

            @tool
            def search_api(query: str) -> str:
                # Searches the API for the query.
                return

            @tool("search", return_direct=True)
            def search_api(query: str) -> str:
                # Searches the API for the query.
                return
    """

    def _make_with_name(tool_name: str) -> Callable:
        def _make_tool(dec_func: Union[Callable, Runnable]) -> BaseTool:
            if isinstance(dec_func, Runnable):
                runnable = dec_func

                if runnable.input_schema.schema().get("type") != "object":
                    raise ValueError("Runnable must have an object schema.")

                async def ainvoke_wrapper(
                    callbacks: Optional[Callbacks] = None, **kwargs: Any
                ) -> Any:
                    return await runnable.ainvoke(kwargs, {"callbacks": callbacks})

                def invoke_wrapper(
                    callbacks: Optional[Callbacks] = None, **kwargs: Any
                ) -> Any:
                    return runnable.invoke(kwargs, {"callbacks": callbacks})

                coroutine = ainvoke_wrapper
                func = invoke_wrapper
                schema: Optional[Type[BaseModel]] = runnable.input_schema
                description = repr(runnable)
            elif inspect.iscoroutinefunction(dec_func):
                coroutine = dec_func
                func = None
                schema = args_schema
                description = None
            else:
                coroutine = None
                func = dec_func
                schema = args_schema
                description = None

            if infer_schema or args_schema is not None:
                return StructuredTool.from_function(
                    func,
                    coroutine,
                    name=tool_name,
                    description=description,
                    return_direct=return_direct,
                    args_schema=schema,
                    infer_schema=infer_schema,
                )
            # If someone doesn't want a schema applied, we must treat it as
            # a simple string->string function
            if func.__doc__ is None:
                raise ValueError(
                    "Function must have a docstring if "
                    "description not provided and infer_schema is False."
                )
            return Tool(
                name=tool_name,
                func=func,
                description=f"{tool_name} tool",
                return_direct=return_direct,
                coroutine=coroutine,
            )

        return _make_tool

    if len(args) == 2 and isinstance(args[0], str) and isinstance(args[1], Runnable):
        return _make_with_name(args[0])(args[1])
    elif len(args) == 1 and isinstance(args[0], str):
        # if the argument is a string, then we use the string as the tool name
        # Example usage: @tool("search", return_direct=True)
        return _make_with_name(args[0])
    elif len(args) == 1 and callable(args[0]):
        # if the argument is a function, then we use the function name as the tool name
        # Example usage: @tool
        return _make_with_name(args[0].__name__)(args[0])
    elif len(args) == 0:
        # if there are no arguments, then we use the function name as the tool name
        # Example usage: @tool(return_direct=True)
        def _partial(func: Callable[[str], str]) -> BaseTool:
            return _make_with_name(func.__name__)(func)

        return _partial
    else:
        raise ValueError("Too many arguments for tool decorator")