Gemini Extension Development

Documentation Delegation

Documentation Source: For authoritative extension syntax and current features, query

gemini-cli-docs

skill. This skill provides development guidance;

gemini-cli-docs

provides official Gemini CLI documentation.

Overview

Expert skill for creating, testing, and distributing Gemini CLI Extensions. Extensions are the primary plugin mechanism for Gemini.

When to Use This Skill

Keywords: gemini extension, create extension, gemini extensions link, extension gallery, context files, extension commands, extension releasing, uninstall extension

Use this skill when:

• Creating a new extension (

  gemini extensions create

  )
• Linking a local extension for development (

  gemini extensions link

  )
• Packaging MCP servers into extensions
• Adding custom slash commands (

  .toml

  ) to extensions
• Installing extensions from GitHub or local paths
• Releasing extensions via Git or GitHub Releases

Extension Anatomy

An extension can contain:

1. extension.yaml

   : Manifest file.

2. GEMINI.md

   : Context "playbook" for the model.

3. package.json

   : Dependencies (if using Node.js/TypeScript). Note: Use the Unified Google Gen AI SDK (e.g.,

   google-genai

   ) as

   google-generativeai

   is deprecated.
4. MCP Servers: Embedded tools.
5. Commands:

   *.toml

   files defining custom slash commands.
6. Tool Restrictions:

   excludeTools

   configuration.

Development Workflow

1. Create:

   gemini extensions create my-extension

2. Link:

   cd my-extension && gemini extensions link .

   (Enables hot-reloading)
3. Test: Run

   gemini

   and use the new capabilities.
4. Publish: Push to GitHub (installable via URL).

Keyword Registry (Delegates to gemini-cli-docs)

create extension

extension template

extension.yaml schema

extension manifest

extension slash commands

toml commands

gemini extensions link

local extension dev

extension releasing git

github release extension

uninstall extension

update extension

Quick Decision Tree

What do you want to do?

1. Start a New Extension -> Query

   gemini-cli-docs

   : "create extension boilerplate"
2. Test Locally -> Query

   gemini-cli-docs

   : "link local extension"
3. Add a Command -> Query

   gemini-cli-docs

   : "define command in extension"
4. Bundle an MCP Server -> Query

   gemini-cli-docs

   : "extension mcp server"
5. Install an Extension -> Query

   gemini-cli-docs

   : "install extension from url"
6. Release an Extension -> Query

   gemini-cli-docs

   : "extension releasing git vs github"

Test Scenarios

Scenario 1: Create Extension

Query: "How do I create a new Gemini CLI extension?" Expected Behavior:

• Skill activates on "create extension"
• Delegates to gemini-cli-docs for template command Success Criteria: User receives

  gemini extensions create

  syntax

Scenario 2: Link for Development

Query: "How do I test my Gemini extension locally?" Expected Behavior:

• Skill activates on "test extension" or "link extension"
• Provides

  gemini extensions link .

  workflow Success Criteria: User receives local development workflow

Scenario 3: Release Extension

Query: "How do I publish my Gemini extension?" Expected Behavior:

• Skill activates on "release extension" or "publish"
• Delegates to docs for Git/GitHub release options Success Criteria: User receives release workflow options

References

Official Documentation: Query

gemini-cli-docs

• "extensions"
• "extension development"

Version History

• v1.1.0 (2025-12-01): Added Test Scenarios section
• v1.0.0 (2025-11-25): Initial release