docs: document tool exclusion from memory via deny policy

[Abhijit-2592]

Summary

This PR updates the policy engine documentation to explain that global deny rules exclude tools from the model's memory (function declarations). It also notes the deprecation of the legacy excludeTools setting.

Details

• Added clarification to docs/reference/policy-engine.md about how deny decisions impact tool visibility for the model.
• Documented that excludeTools in settings.json is deprecated in favor of the Policy Engine's deny rules.
• Verified in packages/core/src/tools/tool-registry.ts that getActiveTools correctly filters these tools.

Related Issues

Closes #21427

How to Validate

1. View the changes in docs/reference/policy-engine.md.
2. Verify that the explanation for deny decisions correctly describes the memory exclusion behavior.
3. Confirm the deprecation note for excludeTools is clear.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run

[gemini-code-assist]

Summary of Changes

Hello, 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 enhances the documentation for the policy engine, providing crucial clarity on how deny rules operate. It specifically details that global deny policies not only block tool execution but also remove those tools entirely from the model's memory, improving security and optimizing context usage. Furthermore, it officially deprecates the older excludeTools setting, consolidating tool exclusion practices under the more robust policy engine framework.

Highlights

• Policy Engine deny rule clarification: Clarified that global deny rules in the policy engine completely exclude tools from the model's memory, enhancing security and saving context window space.
• excludeTools deprecation: Documented the deprecation of the legacy excludeTools setting in settings.json, recommending the use of policy engine deny rules instead.

Activity

• No human activity has been recorded on this pull request yet.

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[github-actions]

Size Change: -4 B (0%)

Total Size: 26 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.5 MB	-4 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

_{compressed-size-action}

[gemini-code-assist]

Code Review

This pull request updates the documentation for the policy engine. It clarifies that global deny rules also remove tools from the model's memory, and it adds a note deprecating the legacy excludeTools setting. While the added details are helpful, the deprecation note is ambiguous as there are multiple settings for excluding tools (tools.exclude, mcpServers.<serverName>.excludeTools). The high-severity comment addressing this ambiguity has been kept as it aligns with the rule for maintaining consistency in documentation, preventing potential user confusion and security misconfigurations.

_{Note: Security Review has been skipped due to the limited scope of the PR.}