Gemini Extensions

This directory contains extensions / MCP (model context protocol) server configurations useful for Chromium development. Each subdirectory within this directory corresponds to one extension.

Configuration are provided in gemini-cli extensions format.

Managing Configurations

Use agents/extensions/install.py to manage extensions. This script is a wrapper around the gemini extensions commands.

Migrating from Project-Level Extensions

If you have previously installed extensions at the project-level, you will be prompted to run the fix command to migrate them to the new user-level model:

bash

vpython3 agents/extensions/install.py fix

Listing Extensions

To see a list of available extensions and their install status:

bash

vpython3 agents/extensions/install.py list

The output table includes the following columns:

EXTENSION: The name of the extension.
AVAILABLE: The version of the extension found in the Chromium source tree. A - indicates it's not available locally.
INSTALLED: The version of the extension currently installed in your Gemini CLI user-level extensions directory. A - indicates it's not installed.
LINKED: Indicates if the installed extension is a symbolic link (yes) to the source directory or a copy (no).
ENABLED: Indicates if the extension is enabled for the current workspace (workspace) or not (-).

Adding Extensions

By default, extensions are installed as links in your user-level extension directory (~/.gemini/extensions).

bash

vpython3 agents/extensions/install.py add <extension_name_1> <extension_name_2>

To copy the extension directory instead of creating a link, use the --copy flag:

bash

vpython3 agents/extensions/install.py add --copy <extension_name_1>

Updating Extensions

bash

vpython3 agents/extensions/install.py update <extension_name>

You can also update all installed extensions at once:

bash

vpython3 agents/extensions/install.py update

Removing Extensions

bash

vpython3 agents/extensions/install.py remove <extension_name>

Types of MCP Servers

There are three types of MCP server configurations supported:

Local MCP Server (chromium tree): The configuration for these servers points to a local MCP server that is located elsewhere within the Chromium source tree.
Local MCP Server (prebuilt): These servers are prebuilt as CIPD packages and located within the same subdirectory as their configuration files.
Remote MCP Server: The configuration for these servers contains a reference to a remote URL where the MCP server is hosted.

Creating an MCP server

See the example server for a minimal example for creating an MCP tool with python and FastMCP