Overview

Duration: 1

Hey there! This codelab walks you through the steps required to convert MCP servers into extensions for Gemini CLI. We begin with creating a super simple MCP server and then convert it to an extension.

Requirements

Duration: 2

In order to follow this codelab, you'll need the following:

Locally installed Gemini CLI
Locally installed Python
(Optional) Astral UV installed locally, to run pip installs faster. If not, just remove uv from the uv pip commands.
(Optional) A Google Cloud Project with billing enabled.

Setup Repo

Duration: 5

Let's setup our repository for the day.

We'll be working with this repository - https://github.com/xprilion/fastmcp-sample

Clone it using:

git clone git@github.com:xprilion/fastmcp-sample.git

Now, let's set it up.

uv venv
source ~/.venv/bin/activate
uv pip install -r requirements.txt

With this done, we're ready to setup Gemini CLI!

Setup Gemini CLI

Duration: 3

Next, we'll setup Gemini CLI.

Follow the installation instructions on this page - https://geminicli.com/docs/get-started/installation/

Whn done, you should be able to run the following command -

gemini

This should bring up the following on your terminal:

Complete the Code

Duration: 15

Now, on your currently active branch of the repo, complete the code parts that come as fill in the blanks!

Run MCP Server

Duration: 2

Great, since you're here, I'll assume you've completed the missing parts of the code! Congratulations!

If not, just switch to the solution branch of the repo and you should be good to run the demo!

For this, you'll need 2 terminal windows.

On the first terminal window, run the following to start the MCP server.

python setup_db.py # <- Run this only once, at first run, then never again

python main.py

This will start the server as shown below:

MCP with Gemini CLI

Duration: 2

Now, you can add the MCP server to your Gemini CLI instance. On a new terminal window, create a Gemini settings configuration with the following commands:

mkdir .gemini
cd .gemini
nano settings.json

And then add the following to that file:

{
  "mcpServers": {
    "todo-server": {
      "httpUrl": "http://localhost:8000/mcp",
      "trust": true
    }
  }
}

After this, if you run the following command:

gemini
/mcp list # <- inside the gemini shell

Then you should see the following tools being displayed as an active MCP server:

In case it shows up as disconnected, retrace your steps.

Deploy the MCP Server

Duration: 2

This step is optional.

Now, you need to deploy the MCP server before you can remotely access it as an extension.

Run the following with gcloud cli installed on your system.

gcloud run deploy

Then follow the prompts on the screen to deploy the repo.

Install as extension

Duration: 5

Head to https://github.com/xprilion/fastmcp-gemini-ext

If you performed the deployment in the previous step, you'll need to follow the instructions on the README of the above Github repo. Else, you can simply use the existing repo.

Run

gemini extensions install https://github.com/xprilion/fastmcp-gemini-ext

This will install the extension to Gemini CLI.

Now, you can again verify the extension installation with

gemini
/extensions list

And get the following output

> /extensions list


Installed extensions:
  todo-ext (v0.1.0) - active (update available)

Conclusion

Duration: 5

Congratulations on making it here! 🎉

In the duration of the codelab you've learnt -

How to create MCP servers with FastMCP
How to deploy MCP servers with Google Cloud Run
How to install Gemini CLI
How to create Gemini CLI Extensions
How to install and use Gemini CLI Extensions

What's Next?

Duration: 1

You can explore the entire codebase here:

and here: