fix(core): prevent inherited docstrings for class-based tools

libs/core/langchain_core/tools/base.py

@@ -189,25 +189,26 @@ def _infer_arg_descriptions(
     *,
     parse_docstring: bool = False,
     error_on_invalid_docstring: bool = False,
-) -> tuple[str, dict]:
-    """Infer argument descriptions from function docstring and annotations.
-
-    Args:
-        fn: The function to infer descriptions from.
-        parse_docstring: Whether to parse the docstring for descriptions.
-        error_on_invalid_docstring: Whether to raise error on invalid docstring.
-
-    Returns:
-        A tuple containing the function description and argument descriptions.
-    """
+) -> tuple[str | None, dict]:
+    """Infer argument descriptions from function docstring and annotations."""
     annotations = typing.get_type_hints(fn, include_extras=True)
+    description: str | None
+    arg_descriptions: dict
+
     if parse_docstring:
         description, arg_descriptions = _parse_python_function_docstring(
             fn, annotations, error_on_invalid_docstring=error_on_invalid_docstring
         )
     else:
-        description = inspect.getdoc(fn) or ""
+        description = inspect.getdoc(fn)
         arg_descriptions = {}
+
+        if inspect.isclass(fn) and description:
+            for parent in fn.__bases__:
+                if inspect.getdoc(parent) == description:
+                    description = None
+                    break
+
     if parse_docstring:
         _validate_docstring_args_against_annotations(arg_descriptions, annotations)
     for arg, arg_type in annotations.items():

libs/core/langchain_core/tools/structured.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import inspect
 import textwrap
 from collections.abc import Awaitable, Callable
 from inspect import signature
@@ -129,10 +130,10 @@ def from_function(
         coroutine: Callable[..., Awaitable[Any]] | None = None,
         name: str | None = None,
         description: str | None = None,
-        return_direct: bool = False,  # noqa: FBT001,FBT002
-        args_schema: ArgsSchema | None = None,
-        infer_schema: bool = True,  # noqa: FBT001,FBT002
         *,
+        return_direct: bool = False,
+        args_schema: ArgsSchema | None = None,
+        infer_schema: bool = True,
         response_format: Literal["content", "content_and_artifact"] = "content",
         parse_docstring: bool = False,
         error_on_invalid_docstring: bool = False,
@@ -189,14 +190,14 @@ def add(a: int, b: int) -> int:
             raise ValueError(msg)
         name = name or source_function.__name__
         if args_schema is None and infer_schema:
-            # schema name is appended within function
             args_schema = create_schema_from_function(
                 name,
                 source_function,
                 parse_docstring=parse_docstring,
                 error_on_invalid_docstring=error_on_invalid_docstring,
                 filter_args=_filter_schema_args(source_function),
             )
+
         description_ = description
         if description is None and not parse_docstring:
             description_ = source_function.__doc__ or None
@@ -213,20 +214,22 @@ def add(a: int, b: int) -> int:
             elif isinstance(args_schema, dict):
                 description_ = args_schema.get("description")
             else:
-                msg = (
-                    "Invalid args_schema: expected BaseModel or dict, "
-                    f"got {args_schema}"
-                )
+                msg = f"""Invalid args_schema: expected BaseModel or
+                    dict, got {args_schema}"""
                 raise TypeError(msg)
+
         if description_ is None:
-            msg = "Function must have a docstring if description not provided."
-            raise ValueError(msg)
+            if inspect.isclass(source_function) and is_basemodel_subclass(
+                source_function
+            ):
+                description_ = ""
+            else:
+                msg = "Function must have a docstring if description not provided."
+                raise ValueError(msg)
+
         if description is 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()}"
         return cls(
             name=name,

libs/core/tests/unit_tests/test_tools.py

@@ -2757,3 +2757,18 @@ def test_tool(
             "type": "array",
         }
     }
+
+
+def test_child_tool_does_not_inherit_docstring() -> None:
+    """Test that a tool subclass does not inherit its parent's docstring."""
+
+    class MyTool(BaseModel):
+        """Parent Tool."""
+
+        foo: str
+
+    @tool
+    class ChildTool(MyTool):
+        bar: str
+
+    assert ChildTool.description == ""  # type: ignore[attr-defined]