[Patch] Dedent docstring (#20959)

Technically a slight prompt breaking change, but I think positive EV in
that it saves tokens and results in more sane / in-distribution prompts

libs/core/langchain_core/tools.py

@@ -21,6 +21,7 @@ from __future__ import annotations
 
 import asyncio
 import inspect
+import textwrap
 import uuid
 import warnings
 from abc import ABC, abstractmethod
@@ -825,16 +826,19 @@ class StructuredTool(BaseTool):
         else:
             raise ValueError("Function and/or coroutine must be provided")
         name = name or source_function.__name__
-        description = description or source_function.__doc__
+        description_ = description or source_function.__doc__
-        if description is None:
+        if description_ is None:
             raise ValueError(
                 "Function must have a docstring if description not provided."
             )
+        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.
         sig = signature(source_function)
-        description = f"{name}{sig} - {description.strip()}"
+        description_ = f"{name}{sig} - {description_.strip()}"
         _args_schema = args_schema
         if _args_schema is None and infer_schema:
             # schema name is appended within function
@@ -844,7 +848,7 @@ class StructuredTool(BaseTool):
             func=func,
             coroutine=coroutine,
             args_schema=_args_schema,  # type: ignore[arg-type]
-            description=description,
+            description=description_,
             return_direct=return_direct,
             **kwargs,
         )

libs/core/tests/unit_tests/test_tools.py

@@ -3,6 +3,7 @@
 import asyncio
 import json
 import sys
+import textwrap
 from datetime import datetime
 from enum import Enum
 from functools import partial
@@ -333,7 +334,7 @@ def test_structured_tool_from_function_docstring() -> None:
 
     prefix = "foo(bar: int, baz: str) -> str - "
     assert foo.__doc__ is not None
-    assert structured_tool.description == prefix + foo.__doc__.strip()
+    assert structured_tool.description == prefix + textwrap.dedent(foo.__doc__.strip())
 
 
 def test_structured_tool_from_function_docstring_complex_args() -> None:
@@ -366,7 +367,7 @@ def test_structured_tool_from_function_docstring_complex_args() -> None:
 
     prefix = "foo(bar: int, baz: List[str]) -> str - "
     assert foo.__doc__ is not None
-    assert structured_tool.description == prefix + foo.__doc__.strip()
+    assert structured_tool.description == prefix + textwrap.dedent(foo.__doc__).strip()
 
 
 def test_structured_tool_lambda_multi_args_schema() -> None:
@@ -701,7 +702,7 @@ def test_structured_tool_from_function() -> None:
 
     prefix = "foo(bar: int, baz: str) -> str - "
     assert foo.__doc__ is not None
-    assert structured_tool.description == prefix + foo.__doc__.strip()
+    assert structured_tool.description == prefix + textwrap.dedent(foo.__doc__.strip())
 
 
 def test_validation_error_handling_bool() -> None: