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

[R-Fischer47]

Description

This PR prevents class-based tools from inheriting the docstring of their parent class. When a child tool class does not have its own docstring, it was incorrectly using the parent's, leading to an inaccurate description for the tool.

This holistic fix modifies two files:

• langchain_core/tools/base.py: The _infer_arg_descriptions function now correctly identifies an inherited docstring and returns None to signal that it should be ignored.
• langchain_core/tools/structured.py: The StructuredTool.from_function method now correctly handles this None signal. It creates the tool with an empty string "" for its description, while still correctly raising an error for regular functions that are missing a docstring.

This ensures that tools have accurate descriptions and that the developer experience is intuitive.

Issue

Fixes #32066

Dependencies

N/A

[codspeed-hq]

CodSpeed Performance Report

Merging #33540 will not alter performance

_{Comparing R-Fischer47:R-Fischer47/stop-tool-docstring-inherit (5fe1542) with master (5489df7)¹}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched
⏩ 21 skipped²

Footnotes

1. No successful run was found on master (90b6805) during the generation of this report, so 5489df7 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩