Rails

Ruby on Rails AI Skill Guide

Overview & Engine Architecture

Rails is a convention-over-configuration full-stack framework: routing maps to controllers, models use Active Record, and views/JSON serializers form the response. Agents follow Rails conventions (folders, generators, callbacks sparingly), keep business rules in models/services rather than fat controllers, and ship schema changes only via migrations.

Router -> Controller -> Model (Active Record)
                \-> Serializer / View -> HTTP
DB <- migrations / schema.rb

When to use this skill

• Building Rails APIs or server-rendered apps
• Adding models, associations, and migrations safely
• Hardening strong parameters and authz (Pundit/CanCanCan)
• Preparing assets/bootsnap for production deploy

Operational directives

1. Prefer generators (rails g model|controller|migration) then edit - stay on rails.
2. Always use strong params; never mass-assign raw params.
3. Put irreversible data fixes in data migrations or rake tasks - not only schema.rb hope.
4. Keep N+1 queries out with includes / preload when listing associations.
5. Use credentials / ENV for secrets - not committed plaintext.

Controller + model sketch

# app/controllers/items_controller.rb
class ItemsController < ApplicationController
  def create
    item = Item.new(item_params)
    if item.save
      render json: item, status: :created
    else
      render json: { errors: item.errors.full_messages }, status: :unprocessable_entity
    end
  end

  private

  def item_params
    params.require(:item).permit(:sku, :qty)
  end
end

# app/models/item.rb
class Item < ApplicationRecord
  validates :sku, presence: true, length: { maximum: 64 }
  validates :qty, numericality: { greater_than_or_equal_to: 0 }
end

Commands

rails new app_name --api
bin/rails db:migrate
bin/rails s
bin/rails test
bin/rails credentials:edit

Common pitfalls

Best practices

• Use Active Job for email and slow I/O; do not block requests.
• Prefer has_many / belongs_to with explicit optional / touch choices.
• Add request specs or system tests for critical flows.
• Match Ruby and Rails majors to what Gemfile.lock and CI install.

Limitations

• Hotwire/Turbo and API-only modes change front-end assumptions.
• Multi-DB and sharding need explicit Rails multi-database config.
• Engines and large monolith modularization are team-specific.

Related skills

• @postgresql - typical primary store for Rails
• @docker - containerizing Puma + assets
• @graphql-apis - GraphQL on Rails when REST is not enough