igmarin/rails-agent-skills

Curated library of 41 public AI agent skills for Ruby on Rails development. Organized by category: planning, testing, code-quality, ddd, engines, infrastructure, api, patterns, context, and orchestration. Covers code review, architecture, security, testing (RSpec), engines, service objects, DDD patterns, and TDD automation. Repository workflows remain documented in GitHub but are intentionally excluded from the Tessl tile.

1.77x

Quality

93%

Does it follow best practices?

Impact

96%

1.77x

Average score across 41 eval scenarios

Securityby

Passed

No known issues

Create Engine — Examples

Name: igmarin/rails-agent-skills
Rating: 95.72 (1 reviews)
Author: igmarin

Extended examples and patterns for engine creation.

Example 1: Mountable Authentication Engine

Scenario: Build an engine that provides authentication (login/logout) to host apps.

Step 1: Scaffold

rails plugin new auth_engine --mountable --full

Step 2: Define Host App Contract

Aspect	Requirement
Host must provide	User model with `email` and `password_digest` attributes; mount route in host routes
Engine exposes	SessionsController, AuthenticationHelper, require_login before_action
Configuration	`user_class` (default: "User"), `session_key` (default: :user_id)

Step 3: Implementation Structure

# lib/auth_engine.rb
require "auth_engine/version"
require "auth_engine/configuration"
require "auth_engine/engine"

module AuthEngine
  class << self
    def configuration
      @configuration ||= Configuration.new
    end

    def configure
      yield(configuration)
    end
  end
end

# lib/auth_engine/configuration.rb
module AuthEngine
  class Configuration
    attr_accessor :user_class, :session_key

    def initialize
      @user_class = "User"
      @session_key = :user_id
    end
  end
end

# lib/auth_engine/engine.rb
module AuthEngine
  class Engine < ::Rails::Engine
    isolate_namespace AuthEngine

    initializer "auth_engine.controller_helpers" do
      ActiveSupport.on_load(:action_controller) do
        include AuthEngine::AuthenticationHelper
      end
    end
  end
end

Step 4: Controller Using Configurable User Class

# app/controllers/auth_engine/sessions_controller.rb
module AuthEngine
  class SessionsController < ApplicationController
    def create
      user = AuthEngine.configuration.user_class.constantize.find_by(email: params[:email])
      if user&.authenticate(params[:password])
        session[AuthEngine.configuration.session_key] = user.id
        redirect_to main_app.root_path
      else
        flash.now[:alert] = "Invalid credentials"
        render :new
      end
    end

    def destroy
      session.delete(AuthEngine.configuration.session_key)
      redirect_to main_app.root_path
    end
  end
end

Step 5: Dummy App Setup

# spec/dummy/config/routes.rb
Rails.application.routes.draw do
  mount AuthEngine::Engine => "/auth"
end

# spec/dummy/app/models/user.rb
class User < ApplicationRecord
  has_secure_password
end

Example 2: Non-Mountable Background Job Engine

Scenario: Engine that provides shared background job processing capabilities.

rails plugin new job_engine --full

Key difference: No routes, no isolate_namespace, but needs Rails initialization hooks.

# lib/job_engine/engine.rb
module JobEngine
  class Engine < ::Rails::Engine
    # No isolate_namespace - jobs live in host app namespace

    initializer "job_engine.configure_queue_adapter" do |app|
      app.config.active_job.queue_adapter = :solid_queue if defined?(SolidQueue)
    end
  end
end

Common Mistakes to Avoid

Mistake	Why It Fails	Correct Approach
`class User < ::User`	Hard-coded host dependency	`config.user_class = "User"` then constantize
Auto-running migrations in initializer	Database errors on boot	Use generators for migrations, never auto-apply
Polluting host app routes	Namespace collision	Use `isolate_namespace` for mountable engines
No dummy app	Can't test integration	Always create dummy app with `rails plugin new`
Config as hash	No validation, hard to document	Config class with explicit attributes

Testing Checklist

See TESTING.md for detailed testing patterns.

Quick verification:

# Inside engine directory
cd spec/dummy
bundle exec rails routes | grep engine_name  # Verify routes
bundle exec rspec spec/requests               # Integration tests
bundle exec rspec spec/lib/configuration_spec # Config tests
grep -r "::User\|::Account" ../lib          # No hard-coded constants

evals

mcp_server

skills

api

context

ddd

infrastructure

orchestration

patterns

planning

testing

workflows

README.md

server.json

tile.json