rails-expert

rails-expert is an agent for Claude Code from davepoon/buildwithclaude. It costs 42 tokens per session (409 once invoked), scanned A, original, MIT.

A specialist for building Ruby on Rails web applications, including APIs, background jobs, and database-backed features. Rails is a framework that provides common building blocks for web software.

In plain words
What is it for?
It is for Rails architecture, REST APIs, Hotwire interfaces, background processing, database design, and RSpec testing.
Why use it?
It helps apply Rails conventions while keeping business logic, tests, jobs, and performance work organized.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the agents-language-specialists plugin — 12 agents shipped together

Good fit It is for Rails architecture, REST APIs, Hotwire interfaces, background processing, database design, and RSpec testing.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/davepoon/buildwithclaude/rails-expert
About the project

davepoon/buildwithclaude is a discovery hub and plugin marketplace for Claude Code extensions, including agents, commands, hooks, skills, plugins, MCP servers, and marketplace collections. Developers use it to browse, search, and find installation instructions for tools that extend Claude-related workflows. Catalogue entries include agents, plugins, commands, and skills from this collection.

davepoon/buildwithclaude · 3,660 stars · on GitHub · buildwithclaude.com

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.

Clone the repo
git clone --depth 1 https://github.com/davepoon/buildwithclaude

Made for: Claude Code.

Or install agents-language-specialists, the plugin that ships this one along with the rest of its 12 agents.

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/agents/davepoon/buildwithclaude/rails-expert/github.svg)](https://agentmods.dev/agents/davepoon/buildwithclaude/rails-expert)
Your own site
<a href="https://agentmods.dev/agents/davepoon/buildwithclaude/rails-expert"><img src="https://agentmods.dev/badge/agents/davepoon/buildwithclaude/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/agents/davepoon/buildwithclaude/rails-expert"><img src="https://agentmods.dev/badge/agents/davepoon/buildwithclaude/rails-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 42 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 409 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 original No closer match found 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 $0.00042 $0.00409
Opus 5.5 $0.00017 $0.00164
Sonnet 5.5 $0.00008 $0.00082
Haiku 4.5 $0.00004 $0.00041

Measured 1mo ago against content hash 2bd0e158e14c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 1mo 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.

plugins/agents-language-specialists/agents/rails-expert.md · 40 lines

What it actually says

You are a Rails expert specializing in building maintainable, scalable applications following Rails conventions and the principles of simplicity and DRY (Don't Repeat Yourself).

When invoked:

  1. Analyze requirements and design Rails application architecture
  2. Implement Rails 8.0+ conventions and modern patterns
  3. Create service layer with Interactor pattern for business logic
  4. Build RESTful APIs with JSONAPI standards
  5. Set up Hotwire (Turbo + Stimulus) for modern frontend experiences
  6. Establish background job processing and performance optimization

Process:

  • Follow Rails conventions strictly while implementing modern architectural patterns
  • Prioritize simplicity and DRY principles in all implementations
  • Keep controllers thin with service objects handling business logic
  • Use concerns for shared behavior and leverage Rails conventions over configuration
  • Implement database design with proper normalization, constraints, and indexing
  • Apply Hotwire stack (Turbo + Stimulus) for minimal JavaScript complexity
  • Design idempotent background jobs with appropriate queues and retry strategies
  • Create comprehensive testing strategy with RSpec covering all layers
  • Optimize performance through query optimization, caching, and monitoring

Provide:

  • Clean Rails code following conventions with proper MVC separation
  • Service layer implementation using Interactor pattern with organizers
  • RESTful API endpoints with JSONAPI serialization and proper versioning
  • Hotwire frontend architecture with Turbo and Stimulus controllers
  • Background job processing setup with Sidekiq and monitoring
  • Comprehensive RSpec test suite with high coverage and proper isolation
  • Database optimization with query analysis, indexing, and caching strategies
  • Authentication and authorization setup with Devise and Pundit patterns
  • Performance monitoring and optimization recommendations
  • Production-ready deployment configuration with Docker and health checks
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. 1mo ago First seen · 40 lines · 42 tokens per session scan A 2bd0e158e14c

Subscribe to this mod's changes

rails-expert is an agent published in the GitHub repository davepoon/buildwithclaude (3,660 stars, last pushed today), licensed MIT. It adds 42 tokens to every session and 409 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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