How to Install Ponytail as a Plugin for Gemini CLI: Complete Setup Guide

Run gemini extensions install https://github.com/DietrichGebert/ponytail to add Ponytail to Gemini CLI, which automatically registers six slash commands and loads the always-on ruleset from AGENTS.md.

Ponytail is a code review extension for Google's Gemini CLI that provides automated analysis through slash commands. When you install Ponytail as a plugin for Gemini CLI, the tool downloads the repository, reads the gemini-extension.json manifest, and makes six specialized commands available in every chat session without requiring additional configuration.

One-Line Installation

Install Ponytail by executing the following command in your terminal, as documented in README.md#L82-L86:

gemini extensions install https://github.com/DietrichGebert/ponytail

This command clones the DietrichGebert/ponytail repository, validates the extension manifest, and registers the plugin with your local Gemini installation.

How the Extension Initialization Works

The installation process leverages three core components from the repository to configure the plugin automatically.

The Extension Manifest (gemini-extension.json)

The gemini-extension.json file serves as the entry point that tells Gemini CLI to:

• Load the always-on ruleset defined in AGENTS.md
• Register the six Ponytail slash commands (/ponytail, /ponytail-review, etc.) as native Gemini skills
• Map the repository's skills/ directory into the CLI's execution context

The Core Instruction Set (AGENTS.md)

Located at the repository root, AGENTS.md contains the rule definitions that Gemini injects into the context window. When you invoke any Ponytail command, these instructions guide the model's response patterns and code review behaviors according to the project's specific guidelines.

Using Ponytail Commands

After installation completes, six slash commands become available in any Gemini chat session, including:

• /ponytail – Activates the default (full) mode for comprehensive analysis
• /ponytail lite – Switches to a faster, lighter mode for quick suggestions
• /ponytail ultra – Enables aggressive suggestion mode for deep refactoring
• /ponytail-review – Runs an automated code review of the current codebase

You can invoke these immediately in new or existing chat sessions:

/ponytail-review   # initiates automated code review

/ponytail ultra    # switches to aggressive suggestion mode

Enabling Always-On Mode

By default, Ponytail loads its ruleset only when you invoke a specific command. To make the AGENTS.md instructions persist across all sessions without explicitly calling a command, copy the rules file into your project's .agents/rules/ directory:

mkdir -p .agents/rules
cp $(gemini config path)/extensions/ponytail/AGENTS.md .agents/rules/

This configuration treats the Ponytail instruction set as a permanent system prompt, applying its guidelines to every interaction within that specific project directory.

Summary

• Installation: Execute gemini extensions install https://github.com/DietrichGebert/ponytail to register Ponytail as a Gemini CLI plugin with zero additional configuration.
• Manifest processing: The gemini-extension.json file automatically configures the extension by referencing AGENTS.md and the skills/ directory.
• Available commands: Six slash commands including /ponytail, /ponytail-review, and operational modes (lite, ultra) become available immediately in chat sessions.
• Always-on setup: Copying AGENTS.md to .agents/rules/ enables persistent rule loading without requiring command invocation.
• Source files: The installation behavior is defined in gemini-extension.json, AGENTS.md, and documented in README.md#L82-L86.

Frequently Asked Questions

Where does Gemini CLI store the Ponytail extension files?

Gemini CLI downloads the repository to your local extensions directory, typically located at $(gemini config path)/extensions/ponytail/. This path contains the full source including AGENTS.md and the skills/ directory referenced by the manifest.

Do I need to restart Gemini CLI after installing Ponytail?

No restart is required. Once the gemini extensions install command completes successfully, the /ponytail commands are immediately available in new and existing chat sessions.

Can I use Ponytail commands in any directory or only in the installation folder?

Ponytail commands work globally within Gemini CLI regardless of your current working directory. However, the optional always-on mode requires copying AGENTS.md to a specific project's .agents/rules/ directory to enable persistent rules for that codebase.

What is the difference between the /ponytail and /ponytail-review commands?

The /ponytail command activates the general assistance mode (with optional lite or ultra variants for adjusting analysis depth), while /ponytail-review specifically triggers an automated code review workflow that analyzes your current codebase against the rules defined in AGENTS.md.

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