x

libs/core/langchain_core/tools/base.py

@@ -434,7 +434,7 @@ class ChildTool(BaseTool):
 
     name: str
     """The unique name of the tool that clearly communicates its purpose."""
-    description: str
+    description: Optional[str] = None
     """Used to tell the model how/when/why to use the tool.
 
     You can provide few-shot examples as a part of the description.

libs/core/langchain_core/tools/structured.py

@@ -39,7 +39,7 @@ if TYPE_CHECKING:
 class StructuredTool(BaseTool):
     """Tool that can operate on any number of inputs."""
 
-    description: str = ""
+    description: Optional[str] = None
     args_schema: Annotated[ArgsSchema, SkipValidation()] = Field(
         ..., description="The tool schema."
     )
@@ -237,21 +237,19 @@ class StructuredTool(BaseTool):
                     f"got {args_schema}"
                 )
                 raise TypeError(msg)
-        if description_ is None:
-            msg = "Function must have a docstring if description not provided."
-            raise ValueError(msg)
-        if description is None:
+        if description is None and description_ is not None:
             # Only apply if using the function's docstring
             description_ = textwrap.dedent(description_).strip()
 
-        # Description example:
-        # search_api(query: str) - Searches the API for the query.
-        description_ = f"{description_.strip()}"
+        if description_:
+            # Always strip description if it exists
+            description_ = description_.strip()
+
         return cls(
             name=name,
             func=func,
             coroutine=coroutine,
-            args_schema=args_schema,
+            args_schema=args_schema,  # type: ignore[arg-type]
             description=description_,
             return_direct=return_direct,
             response_format=response_format,

libs/core/langchain_core/utils/function_calling.py

@@ -22,7 +22,7 @@ from typing import (
 from pydantic import BaseModel
 from pydantic.v1 import BaseModel as BaseModelV1
 from pydantic.v1 import Field, create_model
-from typing_extensions import TypedDict, get_args, get_origin, is_typeddict
+from typing_extensions import NotRequired, TypedDict, get_args, get_origin, is_typeddict
 
 import langchain_core
 from langchain_core._api import beta, deprecated
@@ -48,7 +48,7 @@ class FunctionDescription(TypedDict):
 
     name: str
     """The name of the function."""
-    description: str
+    description: NotRequired[str]
     """A description of the function."""
     parameters: dict
     """The parameters of the function."""

libs/core/tests/unit_tests/test_tools.py

@@ -702,19 +702,21 @@ def test_tool_with_kwargs() -> None:
 
 
 def test_missing_docstring() -> None:
-    """Test error is raised when docstring is missing."""
-    # expect to throw a value error if there's no docstring
-    with pytest.raises(ValueError, match="Function must have a docstring"):
-
-        @tool
-        def search_api(query: str) -> str:
-            return "API result"
+    """Test error is not raised when docstring is missing."""
 
     @tool
-    class MyTool(BaseModel):
-        foo: str
+    def search_api(query: str) -> str:
+        return "API result"
 
-    assert not MyTool.description  # type: ignore[attr-defined]
+    assert search_api.name == "search_api"
+    assert search_api.description is None
+    assert search_api.args_schema
+    assert search_api.args_schema.model_json_schema() == {
+        "properties": {"query": {"title": "Query", "type": "string"}},
+        "required": ["query"],
+        "title": "search_api",
+        "type": "object",
+    }
 
 
 def test_create_tool_positional_args() -> None:

libs/standard-tests/langchain_tests/integration_tests/chat_models.py

@@ -93,7 +93,6 @@ class _MagicFunctionSchema(BaseModel):
 
 @tool(args_schema=_MagicFunctionSchema)
 def magic_function(_input: int) -> int:
-    """Apply a magic function to an input."""
     return _input + 2