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 skills add j4flmao/agent-skills --skill railsgit clone --depth 1 https://github.com/j4flmao/agent-skillsWrote 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/skills/j4flmao/agent-skills/rails)<a href="https://agentmods.dev/skills/j4flmao/agent-skills/rails"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/rails/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.
<a href="https://agentmods.dev/skills/j4flmao/agent-skills/rails"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/rails.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Tool Misuse · line 82 Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
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 | $0.00094 | $0.03875 |
| Opus 5 | $0.00047 | $0.01937 |
| Sonnet 5 | $0.00019 | $0.00775 |
| Haiku 4.5 | $0.00009 | $0.00387 |
Grade A, and why
ruby-rails 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 9d 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 — 544 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Ruby on Rails
Purpose
Build Rails applications with clean MVC separation, service objects, ActiveRecord optimization, API mode conventions, Sidekiq background jobs, and RSpec testing patterns.
Agent Protocol
Trigger
User request includes: Rails, Ruby on Rails, Rails API, ActiveRecord, Rails controller, Rails model, Rails service, Rails job, Rails spec, Rails migration.
Input Context
- Rails version (7.0+, 7.1+)
- Ruby version (3.1+, 3.2+, 3.3+)
- Database (PostgreSQL, MySQL, SQLite)
- Mode (API-only, full MVC)
- Auth (Devise, JWT, OAuth)
- Background jobs (Sidekiq, GoodJob, Solid Queue)
Output Artifact
Controller, model, service object, job class, migration, RSpec test.
Response Format
Produce artifact directly. No preamble, no postamble, no explanations.
Completion Criteria
- Controller delegates to service objects
- ActiveRecord model with scopes, validations, associations
- Service object encapsulates business logic
- Background job with retry configuration
- Request spec covers CRUD with JSON
- Migration with proper indexes
Max Response Length
4096 tokens
Architecture Decision Trees
Service Objects vs PORO Models vs Concerns
| Criterion | Service Object | Fat Model | Concern |
|---|---|---|---|
| Business logic location | app/services/ |
app/models/ |
app/concerns/ |
| Testability | Easy (isolated) | Moderate (needs DB) | Moderate |
| Reusability | High (injectable) | Low (AR callbacks) | Medium (mixed into models) |
| Complexity per unit | Low | High (grows unbound) | Medium |
| Rails conventions | No (manual) | Yes (default) | Yes (Rails 4+) |
Decision: Complex business rules → Service Object. Simple validations/scopes → Model. Cross-model behavior → Concern.
ActiveRecord vs ActiveRecord::Base vs Sequel
| Criterion | ActiveRecord | Sequel | ROM.rb |
|---|---|---|---|
| Rails integration | Native | Adapter | Adapter |
| Performance | Moderate | High | High |
| Query interface | Rich DSL | Sequel DSL | Relation-based |
| Associations | Declarative | Declarative | Explicit |
| Migration system | Built-in | Built-in | Standalone |
What ships with it
8 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.
- references/rails-active-record.md 512 B
- references/rails-api-conventions.md 681 B
- references/rails-api-design.md 71 KB
- references/rails-background-jobs.md 4.0 KB
- references/rails-performance-tuning.md 58 KB
- references/rails-performance.md 2.0 KB
- references/rails-security.md 3.9 KB
- references/rails-testing.md 2.5 KB
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.
- 9d ago First seen · 544 lines · 94 tokens per session scan A 400f569e1d9a
ruby-rails is a skill published in the GitHub repository j4flmao/agent-skills (22 stars, last pushed 2d ago), licensed MIT. It adds 94 tokens to every session and 3,875 once invoked, about $0.0005 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 2026-08-30.
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