[黄耀鑫(Huang Yaoxin) (YaoxinHuang)]

Motivation & Context

tool_call_args_match accepts an omitted argument when its expected value is None, allowing an incorrect tool call to pass local evaluation.

Description & Review Guide

• What are the major changes? Require each expected argument key to exist before comparing its value.
• What is the impact of these changes? Missing null-valued arguments fail evaluation; explicit null and extra arguments retain their existing behavior.
• What do you want reviewers to focus on? The distinction between missing and explicit-null keys, covered for dictionary and JSON-string arguments.

The local evaluation tests, core type checks, pre-commit checks, and package build pass. The full repository test suite was not run.

Related Issue

Fixes #8558

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change.

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Copilot review overview

🟢 Approval recommended

The implementation correctly distinguishes missing keys from explicit null values and includes focused regression coverage.

Review effort: Balanced
Findings: None