# How to Install Ponytail for Gemini CLI: Complete Extension Setup Guide

> Easily install Ponytail for Gemini CLI with this guide. Enhance your Gemini sessions by running the extension install command and unlocking new capabilities.

- Repository: [DietrichGebert/ponytail](https://github.com/DietrichGebert/ponytail)
- Tags: how-to-guide
- Published: 2026-09-07

---

**Install Ponytail for Gemini CLI by running `gemini extensions install https://github.com/DietrichGebert/ponytail`, which registers the extension and makes the `/ponytail` commands and six specialized skills available in your Gemini sessions.**

Ponytail is a Gemini CLI extension that provides "lazy senior dev mode"—a set of always-on rules and commands for code review, technical debt analysis, and over-engineering detection. The extension is packaged as a standard Gemini extension using a manifest file that points to [`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md) for core instructions and automatically discovers commands and skills from the repository structure.

## Understanding the Ponytail Extension Structure

The extension follows Gemini's standard extension format. At the root of the repository, [`gemini-extension.json`](https://github.com/DietrichGebert/ponytail/blob/main/gemini-extension.json) serves as the manifest that registers Ponytail with the CLI.

```json
// gemini-extension.json - defines the extension metadata
{
  "name": "ponytail",
  "version": "1.0.0",
  "description": "Lazy senior dev mode for Gemini CLI",
  "agents": "AGENTS.md"
}

```

This manifest tells Gemini to load always-on rules from [`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md) and automatically discover the `commands/` and `skills/` directories without additional configuration.

## Installation Steps for Gemini CLI

### Step 1: Run the Gemini Extensions Install Command

Execute the standard Gemini CLI extension installation command with the repository URL:

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

```

This pulls the repository, validates the [`gemini-extension.json`](https://github.com/DietrichGebert/ponytail/blob/main/gemini-extension.json) manifest, and registers Ponytail as an active extension. The command is documented in the repository's README under the Gemini CLI section (lines 187-194).

### Step 2: Alternative Installation for Antigravity CLI

Gemini is being rebranded to **Antigravity CLI** (`agy`). The same Ponytail extension works with the new binary using a slightly different command:

```bash
agy plugin install https://github.com/DietrichGebert/ponytail

```

This alternative is documented in the Antigravity CLI subsection (lines 200-206) of the README.

### Step 3: Verify the Installation

Start a new Gemini session and test any Ponytail command:

```text
/ponytail lite

```

A successful installation displays mode confirmation and makes the six Ponytail skills available for the session.

## Available Ponytail Commands and Skills

Once installed, Ponytail provides **four operating modes** via slash commands and **six specialized skills**:

### Operating Modes

| Command | Purpose |
|---------|---------|
| `/ponytail lite` | Minimal overhead, essential checks only |
| `/ponytail full` | All Ponytail checks enabled |
| `/ponytail ultra` | Maximum scrutiny, aggressive flagging |
| `/ponytail off` | Disable Ponytail assistance |

### Built-in Skills

- **`ponytail`** — Core lazy-dev assistance
- **`ponytail-review`** — Over-engineering detection and review
- **`ponytail-audit`** — Code audit and quality assessment
- **`ponytail-debt`** — Technical debt identification
- **`ponytail-gain`** — Value and improvement analysis
- **`ponytail-help`** — Skill documentation and usage help

Invoke skills directly with the skill syntax:

```text
/ponytail-review src/components/Button.tsx

```

## Key Implementation Files

Understanding the source structure helps troubleshoot installation issues:

- **[`gemini-extension.json`](https://github.com/DietrichGebert/ponytail/blob/main/gemini-extension.json)** — Extension manifest defining registration metadata and [`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md) reference
- **[`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md)** — Always-on instruction set applied to every Gemini session with Ponytail active
- **`commands/`** — TOML files defining the `/ponytail` slash commands (lite, full, ultra, off)
- **`skills/ponytail/`** — Implementation of all six Ponytail skills that Gemini autodiscovers

No additional hook files or manual configuration are required—Gemini's extension system handles skill discovery automatically from the `skills/` directory.

## Common Installation Verification

After installation, confirm all components load correctly:

```text

# Test mode switching

/ponytail full

# Test skill invocation

/ponytail-debt src/

```

If commands return "unknown command" errors, verify the extension installed successfully with `gemini extensions list` and re-run the install command if Ponytail does not appear.

## Summary

- **Install Ponytail for Gemini CLI** with `gemini extensions install https://github.com/DietrichGebert/ponytail`
- **Use Antigravity CLI alternative** with `agy plugin install` if running the renamed binary
- **Extension manifest** at [`gemini-extension.json`](https://github.com/DietrichGebert/ponytail/blob/main/gemini-extension.json) registers [`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md) rules and autodiscovers skills
- **Four modes** (lite, full, ultra, off) control Ponytail's assistance level
- **Six skills** provide specialized code review, audit, debt, and gain analysis capabilities
- **No manual configuration** required—Gemini loads commands from `commands/` and skills from `skills/` automatically

## Frequently Asked Questions

### Does Ponytail work with the new Antigravity CLI?

Yes. The same Ponytail extension is compatible with both `gemini` and `agy` binaries. Use `gemini extensions install` for the original CLI or `agy plugin install` for the Antigravity rebranded version. Both commands target the same repository URL.

### Where are Ponytail's always-on rules defined?

The always-on instructions live in [`AGENTS.md`](https://github.com/DietrichGebert/ponytail/blob/main/AGENTS.md) at the repository root. The [`gemini-extension.json`](https://github.com/DietrichGebert/ponytail/blob/main/gemini-extension.json) manifest explicitly references this file, causing Gemini to apply these rules automatically in every session where Ponytail is active—no manual activation needed.

### What happens if the `gemini extensions install` command fails?

Verify you have the latest Gemini CLI version. The extension requires standard Gemini extension support introduced in recent releases. Check `gemini extensions list` to confirm Ponytail appears; if partially installed, run `gemini extensions uninstall ponytail` before reinstalling.

### Can I use individual Ponytail skills without switching modes?

Yes. Skills like `/ponytail-review` and `/ponytail-debt` are directly invocable regardless of the current mode setting. The `/ponytail` mode commands (lite, full, ultra) primarily control the aggressiveness of always-on behavior and background assistance.