feat(cli): expose /tools desc as explicit subcommand for discoverability

[aworki]

What

Add a visible /tools desc subcommand so users can discover description mode directly in TUI command suggestions/help.

Why

Issue #21214 reports that /tools desc behavior exists but is not clearly visible/discoverable from TUI command UX.

How

• Introduced desc (alias: descriptions) as an explicit subcommand under /tools.
• Refactored shared listing logic into a helper to avoid duplication.
• Kept backward compatibility for arg-based usage (/tools desc and /tools descriptions).
• Updated /tools command description to point users to /tools desc.

Testing

• Built required package:
  • npm run build --workspace @google/gemini-cli-core
• Ran focused tests:
  • npm run test --workspace @google/gemini-cli -- src/ui/commands/toolsCommand.test.ts
• Result: 5 passed, 0 failed

Checklist

• Focused single-issue change
• Tests updated and passing
• No unrelated files

Closes #21214

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[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 significantly improves the discoverability of the CLI's tool description feature by introducing a dedicated subcommand. This change makes the functionality more visible within the TUI, addressing a reported user experience issue. The implementation also includes refactoring of existing code to enhance maintainability, all while ensuring that previous methods of accessing this feature remain fully functional.

Highlights

• New Subcommand for Discoverability: Introduced an explicit /tools desc subcommand (with alias /tools descriptions) to enhance the discoverability of the tool description feature directly within the TUI command suggestions and help.
• Code Refactoring: Refactored the shared logic for listing tools into a dedicated listTools helper function to reduce code duplication and improve maintainability.
• Backward Compatibility: Maintained backward compatibility for existing argument-based usage (/tools desc and /tools descriptions) alongside the new subcommand.
• Updated Command Description: Updated the /tools command description to guide users towards the newly introduced /tools desc subcommand for viewing descriptions.

Changelog

• packages/cli/src/ui/commands/toolsCommand.test.ts
  • Added a new test case to verify the existence and correct functionality of the desc subcommand, ensuring it properly displays tool descriptions.
• packages/cli/src/ui/commands/toolsCommand.ts
  • Extracted the core logic for listing tools into a new asynchronous listTools helper function, which now accepts a showDescriptions boolean parameter.
  • Defined toolsDescSubCommand, a new SlashCommand object for the desc subcommand, including its name, aliases, description, and action to call listTools with showDescriptions set to true.
  • Integrated toolsDescSubCommand into the toolsCommand's subCommands array.
  • Modified the toolsCommand's description to inform users about the new desc subcommand.
  • Updated the toolsCommand's action to utilize the new listTools helper, preserving backward compatibility for argument-based description display.

Activity

• The author built the required package.
• Focused tests were run, with 5 tests passing and 0 failing.
• The pull request checklist items were all marked as complete.
• This pull request closes issue give visibility to /tools desc subcommand #21214.

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[gemini-code-assist]

Code Review

This pull request exposes the tool description functionality as an explicit desc subcommand under /tools for better discoverability. The existing logic for listing tools has been refactored into a shared helper function, which is now used by both the new subcommand and the original /tools command action to maintain backward compatibility. A new unit test has been added to cover the new subcommand's functionality. The changes are logical and well-contained. I have reviewed the code and have not found any issues of high or critical severity.

[aworki]

Just a very light follow-up since this PR already has an approval.

If anything is still needed before merge — a rebase, clarification, or adjusting the command naming to better fit repo conventions — I’m happy to handle it.