Document Engine

Use this skill when writing or maintaining documentation for Rails engines.

Core Process & Constraints

Hard gate: All generated documentation MUST satisfy steps 1, 2, and 3 above before proceeding to optional sections.

README snippet (install + mount):

## Installation

Add to your Gemfile:

    gem 'my_engine'

Run:

    bundle install
    rails generate my_engine:install

This creates `config/initializers/my_engine.rb`. Mount the engine in `config/routes.rb`:

    mount MyEngine::Engine, at: '/admin'

Configuration section:

## Configuration

In `config/initializers/my_engine.rb`:

    MyEngine.configure do |config|
      config.user_class = "User"       # required: host model for current user
      config.widget_count = 10         # optional, default 10
    end

Extended Resources

See [CHECKLIST.md](./CHECKLIST.md) for the full recommended README shape and documentation gap checklist. Critical gaps tracked there: installation steps, all config options with defaults, explicit mount path, migration timing, host model/auth assumptions.

• [assets/configuration.md](assets/configuration.md) — detailed config option catalog with type info, validation rules, and all supported defaults
• [assets/examples.md](assets/examples.md) — realistic end-to-end usage examples covering common host-app integration workflows
• [assets/installation.md](assets/installation.md) — step-by-step install and generator reference including post-install setup tasks

Output Style

1. Keep sections short and task-oriented.
2. Validate against CHECKLIST.md: a checklist item passes when the docs contain a corresponding section with at least one copyable code example or explicit prose statement; it fails when absent, incomplete, or lacking a concrete example. Fix each failing item, then re-run from the top. Do not finalize until all critical items pass.
3. Section Delineation: Explicitly label mandatory "Hard-Gate" sections (Installation, Configuration, Host Assumptions) and "Optional" sections (Extension Points, Usage Examples).
4. Upgrade Notes: Include at least one copyable code example in any Upgrade Notes section.
5. Language — Must be in English unless explicitly requested otherwise.

Common pitfalls to avoid:

• Duplicate mount MyEngine::Engine ... across multiple sections — show it only once in the primary installation/mounting section.
• Syntax errors in Ruby/Rails code examples — double-check route mounting and authentication blocks (e.g., authenticate :user, ->(u) { u.admin? } do).

Integration