feat(core): refine Edit and WriteFile tool schemas for Gemini 3

[SandyTao520]

Summary

This PR refines and optimizes the tool schema descriptions for the Edit (replace) and WriteFile tools, specifically for Gemini 3 models. The goal is to reduce token usage, improve clarity, and resolve internal contradictions in the schema definitions.

Details

• Edit (replace) Tool:
  • Removed redundant suggestions to use read_file from the top-level description.
  • Simplified the instruction parameter description by removing verbose 'how-to' sections and examples.
  • Resolved the logic contradiction regarding the old_string context requirement when expected_replacements is used.
  • Cleaned up excessive whitespace and indentation to produce a more compact JSON schema.
  • Updated old_string and new_string descriptions to reflect the strict requirement for unescaped literal text.
• WriteFile Tool:
  • Cleaned up formatting (indentation and newlines) in the tool description.
• Model-Specific Application: These changes are applied exclusively to the Gemini 3 model set in packages/core/src/tools/definitions/model-family-sets/gemini-3.ts. The legacy tool set remains unchanged to preserve historical behavior.
• Snapshot Updates: Updated the model-specific snapshot tests to match the refined descriptions.

Related Issues

Related to #17547, #17546
Relates to #19269

How to Validate

1. Inspect the generated tool schemas for Gemini 3 models to ensure they are more compact and clear.
2. Verify that the legacy models still receive the full, detailed descriptions.
3. Run snapshot tests: npm run test -w @google/gemini-cli-core -- src/tools/definitions/coreToolsModelSnapshots.test.ts

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on MacOS

[gemini-cli]

Hi @SandyTao520, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[gemini-code-assist]

Summary of Changes

Hello @SandyTao520, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on optimizing the tool schema descriptions for the Edit (replace) and WriteFile tools within the Gemini 3 model set. The primary goal is to enhance the efficiency and clarity of these tool definitions by streamlining descriptions, removing redundancies, and resolving logical inconsistencies, thereby improving their utility for large language models while maintaining backward compatibility for other model families.

Highlights

• Tool Schema Refinement: Refined the tool schema descriptions for the Edit (replace) and WriteFile tools, specifically targeting Gemini 3 models.
• Token Usage and Clarity: Reduced token usage and improved clarity in the schema definitions for both Edit and WriteFile tools.
• Contradiction Resolution: Resolved a logical contradiction in the Edit tool schema regarding the old_string context requirement when expected_replacements is used.
• Parameter Description Updates: Simplified the instruction parameter description for the Edit tool and updated old_string and new_string descriptions to emphasize strict unescaped literal text requirements.
• Model-Specific Application: Applied these schema changes exclusively to the Gemini 3 model set, ensuring legacy tool sets remain unchanged.
• Snapshot Updates: Updated model-specific snapshot tests to reflect the refined tool descriptions.

Changelog

• packages/core/src/tools/definitions/snapshots/coreToolsModelSnapshots.test.ts.snap
  • Updated the snapshot for the replace tool, removing redundant suggestions, simplifying the instruction parameter description, and clarifying old_string and new_string requirements.
  • Updated the snapshot for the write_file tool, cleaning up its description formatting.
• packages/core/src/tools/definitions/model-family-sets/gemini-3.ts
  • Simplified the write_file tool description by removing excessive whitespace and newlines.
  • Refined the replace tool description, removing redundant read_file suggestions, simplifying the instruction parameter, and updating old_string and new_string descriptions for clarity and strictness.

Activity

• No specific activity (comments, reviews, or progress updates) was noted in the provided context.

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[gemini-code-assist]

Code Review

This pull request does a great job of refining and optimizing the tool schemas for Edit and WriteFile, specifically for Gemini 3 models. The changes successfully reduce token usage and improve clarity by simplifying descriptions and resolving a key logical contradiction around multiple replacements. The overall direction is excellent. I have one suggestion to further improve the clarity of the replace tool's schema to prevent potential ambiguity for the model.

[github-actions]

Size Change: -2.74 kB (-0.01%)

Total Size: 24.5 MB

Filename	Size	Change
./bundle/gemini.js	24.5 MB	-2.74 kB (-0.01%)

ℹ️ View Unchanged

Filename	Size
./bundle/sandbox-macos-permissive-open.sb	890 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB
./bundle/sandbox-macos-strict-open.sb	4.82 kB
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB

_{compressed-size-action}

[aishaneeshah]

One question/suggestion

[aishaneeshah]

The expected_replacement part is mentioned multiple times - would it make sense to just add "only" here at the higher level description, and remove them from below?

[aishaneeshah]

I think we can still reduce further

"Replaces text within a file. By default, replaces a single occurrence, but can replace multiple occurrences ONLY when `expected_replacements` is specified. This tool requires providing significant context around the change to ensure precise targeting.
The user has the ability to modify the `new_string` content. If modified, this will be stated in the response.

CRITICAL for `old_string`: Include at least 3 lines of context BEFORE and AFTER the target text, matching whitespace and indentation precisely."

WDYT?

[SandyTao520]

Done

[adamfweidman]

LGTM, just remove the .tgz file