gemini-cli

Gemini CLI Extensions

This documentation is up-to-date with the v0.4.0 release.

Gemini CLI extensions package prompts, MCP servers, and custom commands into a familiar and user-friendly format. With extensions, you can expand the capabilities of Gemini CLI and share those capabilities with others. They are designed to be easily installable and shareable.

Extension management

We offer a suite of extension management tools using gemini extensions commands.

Note that these commands are not supported from within the CLI, although you can list installed extensions using the /extensions list subcommand.

Note that all of these commands will only be reflected in active CLI sessions on restart.

Installing an extension

You can install an extension using gemini extensions install with either a GitHub URL source or --path=some/local/path.

Note that we create a copy of the installed extension, so you will need to run gemini extensions update to pull in changes from both locally-defined extensions and those on GitHub.

gemini extensions install https://github.com/gemini-cli-extensions/security

This will install the Gemini CLI Security extension, which offers support for a /security:analyze command.

Uninstalling an extension

To uninstall, run gemini extensions uninstall extension-name, so, in the case of the install example:

gemini extensions uninstall gemini-cli-security

Disabling an extension

Extensions are, by default, enabled across all workspaces. You can disable an extension entirely or for specific workspace.

For example, gemini extensions disable extension-name will disable the extension at the user level, so it will be disabled everywhere. gemini extensions disable extension-name --scope=workspace will only disable the extension in the current workspace.

Enabling an extension

You can enable extensions using gemini extensions enable extension-name. You can also enable an extension for a specific workspace using gemini extensions enable extension-name --scope=workspace from within that workspace.

This is useful if you have an extension disabled at the top-level and only enabled in specific places.

Updating an extension

For extensions installed from a local path or a git repository, you can explicitly update to the latest version (as reflected in the gemini-extension.json version field) with gemini extensions update extension-name.

You can update all extensions with:

gemini extensions update --all

Extension creation

We offer commands to make extension development easier.

Create a boilerplate extension

We offer several example extensions context, custom-commands, exclude-tools and mcp-server. You can view these examples here.

To copy one of these examples into a development directory using the type of your choosing, run:

gemini extensions new path/to/directory custom-commands

Link a local extension

The gemini extensions link command will create a symbolic link from the extension installation directory to the development path.

This is useful so you don’t have to run gemini extensions update every time you make changes you’d like to test.

gemini extensions link path/to/directory

How it works

On startup, Gemini CLI looks for extensions in <home>/.gemini/extensions

Extensions exist as a directory that contains a gemini-extension.json file. For example:

<home>/.gemini/extensions/my-extension/gemini-extension.json

gemini-extension.json

The gemini-extension.json file contains the configuration for the extension. The file has the following structure:

{
  "name": "my-extension",
  "version": "1.0.0",
  "mcpServers": {
    "my-server": {
      "command": "node my-server.js"
    }
  },
  "contextFileName": "GEMINI.md",
  "excludeTools": ["run_shell_command"]
}

• name: The name of the extension. This is used to uniquely identify the extension and for conflict resolution when extension commands have the same name as user or project commands. The name should be lowercase or numbers and use dashes instead of underscores or spaces. This is how users will refer to your extension in the CLI. Note that we expect this name to match the extension directory name.
• version: The version of the extension.
• mcpServers: A map of MCP servers to configure. The key is the name of the server, and the value is the server configuration. These servers will be loaded on startup just like MCP servers configured in a settings.json file. If both an extension and a settings.json file configure an MCP server with the same name, the server defined in the settings.json file takes precedence.
  • Note that all MCP server configuration options are supported except for trust.
• contextFileName: The name of the file that contains the context for the extension. This will be used to load the context from the extension directory. If this property is not used but a GEMINI.md file is present in your extension directory, then that file will be loaded.
• excludeTools: An array of tool names to exclude from the model. You can also specify command-specific restrictions for tools that support it, like the run_shell_command tool. For example, "excludeTools": ["run_shell_command(rm -rf)"] will block the rm -rf command. Note that this differs from the MCP server excludeTools functionality, which can be listed in the MCP server config.

When Gemini CLI starts, it loads all the extensions and merges their configurations. If there are any conflicts, the workspace configuration takes precedence.

Custom commands

Extensions can provide custom commands by placing TOML files in a commands/ subdirectory within the extension directory. These commands follow the same format as user and project custom commands and use standard naming conventions.

Example

An extension named gcp with the following structure:

.gemini/extensions/gcp/
├── gemini-extension.json
└── commands/
    ├── deploy.toml
    └── gcs/
        └── sync.toml

Would provide these commands:

• /deploy - Shows as [gcp] Custom command from deploy.toml in help
• /gcs:sync - Shows as [gcp] Custom command from sync.toml in help

Conflict resolution

Extension commands have the lowest precedence. When a conflict occurs with user or project commands:

1. No conflict: Extension command uses its natural name (e.g., /deploy)
2. With conflict: Extension command is renamed with the extension prefix (e.g., /gcp.deploy)

For example, if both a user and the gcp extension define a deploy command:

• /deploy - Executes the user’s deploy command
• /gcp.deploy - Executes the extension’s deploy command (marked with [gcp] tag)

Variables

Gemini CLI extensions allow variable substitution in gemini-extension.json. This can be useful if e.g., you need the current directory to run an MCP server using "cwd": "${extensionPath}${/}run.ts".

Supported variables:

variable	description
${extensionPath}	The fully-qualified path of the extension in the user’s filesystem e.g., ‘/Users/username/.gemini/extensions/example-extension’. This will not unwrap symlinks.
${workspacePath}	The fully-qualified path of the current workspace.
${/} or ${pathSeparator}	The path separator (differs per OS).

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