rails-expert

rails-expert is a skill for Claude Code, Codex from eric861129/SKILLS_All-in-one. It costs 104 tokens per session (1,323 once invoked), scanned A, a copy of rails-expert, MIT.

A Ruby on Rails development guide for building web applications with Rails 7 or newer, including database-backed pages, live updates, background jobs, and automated tests.

In plain words
What is it for?
Use it to create models, controllers, migrations, Turbo interfaces, WebSocket features, Sidekiq jobs, RSpec tests, and query optimizations.
Why use it?
It helps structure Rails features and find common problems such as slow database queries or repeated queries for related records.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to create models, controllers, migrations, Turbo interfaces, WebSocket features, Sidekiq jobs, RSpec tests, and query optimizations.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/eric861129/skills_all-in-one/rails-expert
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add eric861129/SKILLS_All-in-one --skill rails-expert
Clone the repo
git clone --depth 1 https://github.com/eric861129/SKILLS_All-in-one

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for rails-expert

README.md
[![agentmods](https://agentmods.dev/badge/skills/eric861129/skills_all-in-one/rails-expert/github.svg)](https://agentmods.dev/skills/eric861129/skills_all-in-one/rails-expert)
Your own site
<a href="https://agentmods.dev/skills/eric861129/skills_all-in-one/rails-expert"><img src="https://agentmods.dev/badge/skills/eric861129/skills_all-in-one/rails-expert/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for rails-expert

Your own site · 80×15
<a href="https://agentmods.dev/skills/eric861129/skills_all-in-one/rails-expert"><img src="https://agentmods.dev/badge/skills/eric861129/skills_all-in-one/rails-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 104 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,323 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 94% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00104 $0.01323
Opus 5 $0.00052 $0.00661
Sonnet 5 $0.00021 $0.00265
Haiku 4.5 $0.00010 $0.00132

Measured 8d ago against content hash 1579515f3ad2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

rails-expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

94% identical to rails-expert — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

public/SKILLS/Development & Code Tools/rails-expert/SKILL.md · 155 lines

How it starts

The opening of the file, as written. The whole thing — 155 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Rails Expert

Core Workflow

  1. Analyze requirements — Identify models, routes, real-time needs, background jobs
  2. Scaffold resourcesrails generate model User name:string email:string, rails generate controller Users
  3. Run migrationsrails db:migrate and verify schema with rails db:schema:dump
    • If migration fails: inspect db/schema.rb for conflicts, rollback with rails db:rollback, fix and retry
  4. Implement — Write controllers, models, add Hotwire (see Reference Guide below)
  5. Validatebundle exec rspec must pass; bundle exec rubocop for style
    • If specs fail: check error output, fix failing examples, re-run with --format documentation for detail
    • If N+1 queries surface during review: add includes/eager_load (see Common Patterns) and re-run specs
  6. Optimize — Audit for N+1 queries, add missing indexes, add caching

Reference Guide

Load detailed guidance based on context:

Topic Reference Load When
Hotwire/Turbo references/hotwire-turbo.md Turbo Frames, Streams, Stimulus controllers
Active Record references/active-record.md Models, associations, queries, performance
Background Jobs references/background-jobs.md Sidekiq, job design, queues, error handling
Testing references/rspec-testing.md Model/request/system specs, factories
API Development references/api-development.md API-only mode, serialization, authentication

Common Patterns

N+1 Prevention with includes/eager_load

# 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 })

Turbo Frame Setup (partial page update)

<%# 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 %>

Read the full file on GitHub · 155 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 155 lines · 104 tokens per session scan A 1579515f3ad2

Subscribe to this mod's changes

rails-expert is a skill published in the GitHub repository eric861129/SKILLS_All-in-one (52 stars, last pushed 4mo ago), licensed MIT. It adds 104 tokens to every session and 1,323 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to rails-expert, differing in 2 lines, and is treated as a copy.