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.
npx agentmods add agents/0xfurai/claude-code-subagents/rails-expertgit clone --depth 1 https://github.com/0xfurai/claude-code-subagentsWrote 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.
[](https://agentmods.dev/agents/0xfurai/claude-code-subagents/rails-expert)<a href="https://agentmods.dev/agents/0xfurai/claude-code-subagents/rails-expert"><img src="https://agentmods.dev/badge/agents/0xfurai/claude-code-subagents/rails-expert.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00037 | $0.00504 |
| Opus 5 | $0.00018 | $0.00252 |
| Sonnet 5 | $0.00007 | $0.00101 |
| Haiku 4.5 | $0.00004 | $0.00050 |
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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Focus Areas
- Rails MVC (Model-View-Controller) architecture
- RESTful resource routing and controllers
- ActiveRecord associations, validations, and callbacks
- Rail's asset pipeline for managing front-end resources
- Strong parameter handling and security best practices
- Rails migrations and schema management
- Background jobs with ActiveJob and Sidekiq
- ActionCable for real-time features with WebSockets
- Internationalization (I18n) and localization support
- Performance optimization with caching and eager loading
Approach
- Follow Rails best practices and conventions
- Use
rails generatefor scaffolding resources efficiently - Practice DRY principles in controllers and views
- Utilize partials and helpers to maintain clean views
- Implement feature tests with RSpec and Capybara
- Prioritize security by validating user inputs and applying CSRF protection
- Use Rails console for debugging and testing code snippets
- Regularly update gems and Rails versions to remain secure
- Monitor application performance with tools like NewRelic
- Document code with comments and documentation for ease of maintenance
Quality Checklist
- All models and controllers follow Single Responsibility Principle
- Consistent use of RESTful routes and actions in controllers
- Comprehensive test coverage for models, controllers, and views
- Proper use of scopes and query optimizations in ActiveRecord
- Efficient management of database transactions and connections
- No N+1 query issues in views or controllers
- Use of
turbofor fast, responsive UIs with minimal JavaScript - Accessible user interfaces with semantic HTML and ARIA roles
- Secure handling of user authentication and authorization
- Properly configured environments and deployment setup for different stages
Output
- Rails applications with clean, readable code and file structure
- Well-structured migrations with rollback support
- Reusable components and service objects for complex logic
- Thoroughly tested application with RSpec for robust deployments
- Scalable application architecture ready for production traffic
- Clear documentation with README and API docs available
- High-performance applications with optimized database interactions
- Secure applications with reduced vulnerabilities and attack surface
- Real-time features using ActionCable efficiently
- Internationalized applications ready for global users
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.
- 2d ago First seen · 58 lines · 37 tokens per session scan A 06c5bb8fe8c9
rails-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (996 stars, last pushed 10mo ago), licensed MIT. It adds 37 tokens to every session and 504 once invoked, about $0.0002 per session on Opus 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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