# Extension Development

Build, install, and hot-reload Nimbalyst extensions using MCP tools.

- Repository: https://github.com/nimbalyst/nimbalyst (2013 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-31
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add nimbalyst/nimbalyst --skill extension-development -g -a claude-code -y`
Codex: `npx skills add nimbalyst/nimbalyst --skill extension-development -g -a codex -y`
Cursor: `npx skills add nimbalyst/nimbalyst --skill extension-development -g -a cursor -y`
Gemini CLI: `npx skills add nimbalyst/nimbalyst --skill extension-development -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add nimbalyst/nimbalyst`

## Description

Build, install, and hot-reload Nimbalyst extensions using MCP tools. Use when developing, testing, or iterating on Nimbalyst extensions.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Extension Development in Nimbalyst

Nimbalyst provides MCP tools for building, installing, and hot-reloading extensions directly from within the running app. This enables rapid iteration on extension development without manually running build commands.

The recommended in-app scaffold flow uses `File > New Extension Project`, `Developer > New Extension Project`, or the Extension Developer Kit's `/new-extension` command. Enable Extension Dev Tools in Settings > Advanced before using the build/install workflow.

## Available MCP Tools

### Build Extension
```
mcp__nimbalyst-extension-dev__extension_build
```
Runs the project's `build` script (usually vite build) with pnpm if the project uses pnpm, npm otherwise.

**Parameters:**
- `path`: Absolute path to the extension project root (directory containing package.json and manifest.json)

**Returns:** Build output including any errors or warnings.

### Install Extension
```
mcp__nimbalyst-extension-dev__extension_install
```
Installs a built extension into the running Nimbalyst instance. The extension must be built first.

**Parameters:**
- `path`: Absolute path to the extension project root

**Returns:** Installation status and any validation warnings.

### Hot Reload Extension
```
mcp__nimbalyst-extension-dev__extension_reload
```
Rebuilds and reinstalls an extension in one step. This is the most common tool for iterating on extension development.

**Parameters:**
- `extensionId`: The extension ID from manifest.json (e.g., "com.nimbalyst.my-extension")
- `path`: Absolute path to the extension project root

**Returns:** Build and reload status.

### Uninstall Extension
```
mcp__nimbalyst-extension-dev__extension_uninstall
```
Removes an installed extension from the running Nimbalyst instance.

**Parameters:**
- `extensionId`: The extension ID to uninstall

The rest: https://github.com/nimbalyst/nimbalyst/blob/HEAD/packages/extensions/extension-dev-kit/claude-plugin/skills/extension-development/SKILL.md