Gemini CLI Skill

Use Google’s gemini CLI as an external “second brain” when you need a very large context window, a second opinion, or safe sandbox execution. This skill does not use MCP; it runs the local CLI directly.

When To Use

Use this skill when the user asks to:

• “Ask Gemini” / “Use Gemini”
• Analyze or summarize large files or directories (especially with @path references)
• Brainstorm options with a specific framework (SCAMPER, design thinking, etc.)
• Generate structured edit suggestions (“change mode”) that can be applied deterministically

Prerequisites

• gemini CLI is installed and configured (e.g. gemini --version works)
• You are allowed to run local shell commands in this environment
• For sandbox execution, Gemini CLI supports -s/--sandbox (see gemini --help)

Core Commands

One-shot query (plain)

gemini "Explain what this code does: @src/main.ts"

Choose a model

gemini -m gemini-3-pro-preview "..."
gemini -m gemini-3-flash-preview "..."

Sandbox mode

gemini -s "Safely test @scripts/example.py and explain the results."

Helper Script (Recommended)

This skill ships with a dependency-free wrapper that mirrors the core behavior of gemini-mcp-tool without MCP:

skills/gemini-cli/scripts/gemini-tool.mjs

Important: Gemini CLI can only read files under its current “project directory” (typically the process working directory). Run the wrapper from the repo you want Gemini to read, or pass --cwd.

node skills/gemini-cli/scripts/gemini-tool.mjs help

Ask Gemini (wrapper)

node skills/gemini-cli/scripts/gemini-tool.mjs ask --prompt "Summarize @. in 5 bullets."
node skills/gemini-cli/scripts/gemini-tool.mjs ask --cwd /path/to/project --prompt "Summarize @. in 5 bullets."
node skills/gemini-cli/scripts/gemini-tool.mjs ask --prompt "..." --model gemini-3-pro-preview
node skills/gemini-cli/scripts/gemini-tool.mjs ask --prompt "..." --sandbox

Brainstorm (wrapper)

node skills/gemini-cli/scripts/gemini-tool.mjs brainstorm --prompt "How should we design onboarding?" --methodology scamper --ideaCount 12

Change Mode (structured edits + chunk caching)

Use change mode when you want Gemini to output deterministic OLD/NEW blocks that can be applied by exact string matching.

node skills/gemini-cli/scripts/gemini-tool.mjs ask --changeMode --prompt "In @src/foo.ts, rename Foo to Bar and update call sites."

If the response is chunked, the output includes a cacheKey. Fetch the next chunk:

node skills/gemini-cli/scripts/gemini-tool.mjs fetch-chunk --cacheKey <key> --chunkIndex 2

Safety Rules

• Never execute destructive commands from Gemini output without explicit user approval.
• In change mode, the OLD block must match the file content exactly; otherwise, do not apply the edit.
• Prefer read-only analysis unless the user explicitly requests changes.