Fix args_to_skip validation failure for dict type parameters

[rasdani]

Description

• Filters function signature before schema generation to avoid strict JSON schema validation errors on skipped parameters
• Parameters with dict type (which produce additionalProperties: true) no longer cause validation failures when listed in args_to_skip

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Test improvement

Testing

• All existing tests pass when running uv run pytest locally.
• New tests have been added to cover the changes

Checklist

• My code follows the style guidelines of this project as outlined in AGENTS.md
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

---

Note

Fixes schema generation for skipped tool args by filtering function signatures before conversion.

• Introduces filter_signature to remove skipped params (and annotations, incl. self) prior to convert_func_to_oai_tool
• Updates StatefulToolEnv.add_tool to use the filtered signature so dict-typed skipped args no longer appear in parameters
• Adds test test_add_tool_skips_dict_type_args verifying dict param omission from the schema

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[cursor]

filter_signature mutates original function signature permanently

The filter_signature function permanently modifies the original function's __signature__ and __annotations__ attributes in place. This causes side effects when the same function is reused elsewhere or added to multiple StatefulToolEnv instances with different args_to_skip. For example, if add_tool(my_func, args_to_skip=["a"]) is called, then my_func is permanently altered, so any subsequent inspection or use of that function will see the modified signature. This affects module-level functions (like secret_tool in tests) and bound methods. The function should work on a copy or wrapper rather than mutating the original.