How to Use Gemini CLI Extensions to Power Up Your Developer Workflow

Introduction

Hey fellow devs! 🚀 If you’ve been exploring Gemini CLI already (or heard the buzz), one of the most exciting features is extensions, think of them as power-ups for your command line. With extensions, you can plug in tools you already use (databases, API clients, design tools, etc.), wrap them in intelligent prompts, and make Gemini CLI truly yours.

In this post, I’ll walk you through:

• What Gemini CLI extensions are
• Why you’d want them
• How to install & build your own
• Real developer workflow examples
• Tips, pitfalls, and future ideas

Let’s jump in!

What Are Gemini CLI Extensions?

Gemini CLI extensions let you expand and customize what your CLI AI agent can do. Instead of only using the built-in capabilities, you can bundle:

• Custom commands (slash commands)
• MCP servers (connections to external services)
• Context files (instruction files like GEMINI.md)
• Tool exclusions or overrides

These extensions live in your .gemini/extensions folder (or globally in your home directory). On startup, Gemini CLI merges extension config into its runtime, so the new commands and integrations are available automatically. Google Gemini+2GitHub+2

In short: extensions let you tailor Gemini to your exact workflow, not the other way around.

Why Use Extensions? (Benefits You’ll Love)

Here’s where this gets fun (and practical):

• Bring your favorite tools inside your AI environment — Think Figma, Postman, security scans, database queries, all accessible from the terminal.
• Reusable logic & prompts — Package repetitive, complex prompts into simple slash commands your team can use.
• Smarter context awareness — Extensions can include files or instructions so Gemini “knows” your project norms.
• Safe customization — You can disable risky built-in tools (e.g. run_shell_command) or tailor what the AI is allowed to do.
• Ecosystem & sharing — Share your extensions (open-source or internally) so others can benefit from your workflows.

As Google puts it: “Extensions are power-ups — pre-packaged integrations to connect Gemini CLI to external tools with minimal setup.” Google Gemini+1

Also, major players like Stripe, Shopify, Elastic, Postman, and Snyk are already launching extensions for their services. blog.google

How to Use Existing Extensions (Install & Run)

Let’s get hands-on:

1. Install an extension

You can install either from a GitHub URL or a local path:

gemini extensions install https://github.com/your-favorite/ext-repo

Or:

gemini extensions install --path=./my-local-extension

Note: Gemini makes a copy of the extension into your .gemini/extensions directory. To update, you’ll run gemini extensions update. Google Gemini

2. Uninstall / update

To remove:

gemini extensions uninstall extension-name

To update:

gemini extensions update extension-name
gemini extensions update --all

Local or Git-based extensions will reflect new versions if defined in their gemini-extension.json. Google Gemini

3. Link a local extension for development

When you’re building an extension, you don’t want to reinstall repeatedly. Use:

gemini extensions link /path/to/your/extension

This symlinks it, so changes reflect immediately without reinstall. Google Gemini

Building Your Own Gemini CLI Extension

Now the fun part: making your own. Here’s a streamlined path:

1. Create extension scaffold

Gemini offers some built-in templates (e.g. for custom-commands, context, mcp-server, exclude-tools). Use:

gemini extensions new path/to/dir custom-commands

This gives you the skeleton. Google Gemini

2. Define your gemini-extension.json

This file configures your extension. A sample:

{
  "name": "my-awesome-ext",
  "version": "0.1.0",
  "mcpServers": {
    "my-server": {
      "command": "node server.js"
    }
  },
  "contextFileName": "MYEXT.md",
  "excludeTools": ["run_shell_command(rm -rf)"]
}

Explanation:

• name & version: identifies your extension
• mcpServers: define extra servers (if your extension needs a backend)
• contextFileName: a file in your extension folder that gives extra instructions
• excludeTools: disable built-in tools or specific commands for safety Google Gemini

3. Add custom commands

You can create .toml files under commands/ to define Slash commands. Example:

commands/deploy.toml:

description = "Deploy this project to staging"
prompt = """
You are a deployment assistant. Based on the current branch, deploy this project to the staging server.
"""

This makes /deploy available in the Gemini CLI. Google Gemini

4. Context & instructions

Include a MYEXT.md or any .md file (matching contextFileName) with instructions, usage guidelines, or style rules. That gives the AI more precise behavior. Google Gemini

5. Test & iterate

Link your extension (or reinstall) and reload Gemini CLI. Check that your slash commands show up and they behave. Iterate by refining prompt logic and capabilities.

Real Workflow Examples & Ideas

Here’s how you can use extensions right now to boost your dev flow:

• Security checks — Create /security:analyze that scans your diff with Snyk API and returns vulnerabilities.
• Database introspection — /db:describe users queries an MCP server to fetch table schema.
• Design to code — Use Figma extension to fetch a frame and generate a React component from it.
• Stripe helper — /stripe:create-invoice customer-id that calls Stripe API under the hood.
• Internal tools bridging — Expose your company’s private API or CLI via extension, so Gemini can interface with them naturally.

These let you speak your workflow, not force your workflow into the tool.

Tips, Best Practices & Gotchas

Tip	Why It Matters
Keep commands focused & narrow	Smaller prompts are more reliable and maintainable
Be cautious with tool permissions	Use excludeTools or limit shell commands to avoid harm
Version carefully	Use version in gemini-extension.json so users can update cleanly
Use linking in dev	So you don’t have to reinstall for each change
Fallback behaviors	If external service fails, handle gracefully in your prompt logic

Also: extensions are merged on startup from global + workspace. If there’s a conflict, the workspace config wins. Google Gemini

What’s Coming / Future Potential

• A richer marketplace / catalog of community & partner extensions
• Deeper integration with Gemini Code Assist (IDE mode)
• Sharing and monetizing custom extensions
• Smarter discovery & versioning within the ecosystem
• Better debugging, logging, and tooling around extension development

Gemini’s open-source nature and support for Model Context Protocol (MCP) make it a flexible foundation for this evolving ecosystem. Ars Technica+1

Conclusion

Gemini CLI extensions change how we think about AI in the terminal: it’s no longer just a fixed agent — it’s a modular, extensible system you shape around your own workflow. Whether you’re automating internal APIs, weaving in design tools, or just saving time on repeated prompts, extensions let Gemini CLI speak your language.

Start by trying or installing some existing extensions. Then, build your own for your use case. Over time, your dev environment will adapt to you, not the other way around.