Rails Expert

What it does

When your agent uses it

• Building a Rails 7 app with Turbo Frames and Turbo Streams
• Fixing N+1 queries with includes or eager_load
• Adding Sidekiq background jobs for email or other slow work
• Setting up Action Cable for real-time updates
• Writing RSpec model, request and system specs

Example prompts

• “Generate a Post model and controller with an author association, then fix the N+1 on the index page.”
• “Make the comments list update in place with a Turbo Frame when a new comment is posted.”
• “Move the welcome email into a background job and cover it with an RSpec spec.”
• “Run rubocop and rspec and fix whatever fails.”

Requirements

• A Rails 7+ project with RSpec and RuboCop

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Analyze requirements — Identify models, routes, real-time needs, background jobs
2. 2Scaffold resources — rails generate model User name:string email:string, rails generate controller Users
3. 3Run migrations — rails db:migrate and verify schema with rails db:schema:dump
4. 4Implement — Write controllers, models, add Hotwire (see Reference Guide below)
5. 5Validate — bundle exec rspec must pass; bundle exec rubocop for style
6. 6Optimize — Audit for N+1 queries, add missing indexes, add caching

What it can do on your machine

Read from SKILL.md and the folder at commit 1be15d8. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • rails
  • bundle

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • github.com
  • synergetic.solutions
  • jeffallan.github.io

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Rails Expert loads about 1.4k tokens when it runs, and up to ~9.8k if it reads all its reference files. Until then it costs about 130 tokens; SKILL.md has 319 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~130

When it runs · the whole SKILL.md, loaded when a task matches

~1.4k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~9.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Jeffallan/claude-skills at commit 1be15d8, republished under its MIT licence (© Jeffallan). 319 words, ~1,416 tokens.

name

rails-expert

description

Rails 7+ specialist that optimizes Active Record queries with includes/eager_load, implements Turbo Frames and Turbo Streams for partial page updates, configures Action Cable for WebSocket connections, sets up Sidekiq workers for background job processing, and writes comprehensive RSpec test suites. Use when building Rails 7+ web applications with Hotwire, real-time features, or background job processing. Invoke for Active Record optimization, Turbo Frames/Streams, Action Cable, Sidekiq, RSpec Rails.

license

MIT

metadata.author

https://github.com/Jeffallan

metadata.company

https://synergetic.solutions

metadata.version

1.1.0

metadata.domain

backend

metadata.triggers

Rails, Ruby on Rails, Hotwire, Turbo Frames, Turbo Streams, Action Cable, Active Record, Sidekiq, RSpec Rails

metadata.role

specialist

metadata.scope

implementation

metadata.output-format

code

metadata.related-skills

fullstack-guardian, database-optimizer

# BAD — triggers N+1
posts = Post.all
posts.each { |post| puts post.author.name }

# GOOD — eager load association
posts = Post.includes(:author).all
posts.each { |post| puts post.author.name }

# GOOD — eager_load forces a JOIN (useful when filtering on association)
posts = Post.eager_load(:author).where(authors: { verified: true })

<%# app/views/posts/index.html.erb %>
<%= turbo_frame_tag "posts" do %>
  <%= render @posts %>
  <%= link_to "Load More", posts_path(page: @next_page) %>
<% end %>

<%# app/views/posts/_post.html.erb %>
<%= turbo_frame_tag dom_id(post) do %>
  <h2><%= post.title %></h2>
  <%= link_to "Edit", edit_post_path(post) %>
<% end %>

# app/controllers/posts_controller.rb
def index
  @posts = Post.includes(:author).page(params[:page])
  @next_page = @posts.next_page
end

# app/jobs/send_welcome_email_job.rb
class SendWelcomeEmailJob < ApplicationJob
  queue_as :default
  sidekiq_options retry: 3, dead: false

  def perform(user_id)
    user = User.find(user_id)
    UserMailer.welcome(user).deliver_now
  rescue ActiveRecord::RecordNotFound => e
    Rails.logger.warn("SendWelcomeEmailJob: user #{user_id} not found — #{e.message}")
    # Do not re-raise; record is gone, no point retrying
  end
end

# Enqueue from controller or model callback
SendWelcomeEmailJob.perform_later(user.id)

# app/controllers/posts_controller.rb
class PostsController < ApplicationController
  before_action :set_post, only: %i[show edit update destroy]

  def create
    @post = Post.new(post_params)
    if @post.save
      redirect_to @post, notice: "Post created."
    else
      render :new, status: :unprocessable_entity
    end
  end

  private

  def set_post
    @post = Post.find(params[:id])
  end

  def post_params
    params.require(:post).permit(:title, :body, :published_at)
  end
end

© Jeffallan, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (references) in skills/rails-expert of Jeffallan/claude-skills.

• SKILL.md
• references/active-record.md
• references/api-development.md
• references/background-jobs.md
• references/hotwire-turbo.md
• references/rspec-testing.md

Open the folder on GitHubat commit 1be15d8