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 sandeepmvl/rails-skills --skill 00-rails-project-discoverygit clone --depth 1 https://github.com/sandeepmvl/rails-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/sandeepmvl/rails-skills/00-rails-project-discovery)<a href="https://agentmods.dev/skills/sandeepmvl/rails-skills/00-rails-project-discovery"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/00-rails-project-discovery/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/sandeepmvl/rails-skills/00-rails-project-discovery"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/00-rails-project-discovery.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00158 | $0.04604 |
| Opus 5 | $0.00079 | $0.02302 |
| Sonnet 5 | $0.00032 | $0.00921 |
| Haiku 4.5 | $0.00016 | $0.00460 |
Grade A, and why
rails-project-discovery 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 12d 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 — 260 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Project Discovery
Entry point for the
rails-skillspack. Interview the developer in a short structured way, then load the right downstream skills. Do not start writing Rails code, generating files, or runningrails newuntil the interview is complete and the relevant downstream skills are loaded.
Why this skill exists
AI coding agents fail at Rails not because they don't know Ruby syntax — they fail because they don't know which Rails the user is on. A rails new for a Hotwire monolith looks nothing like a Rails-API + React SPA. A Rails 4 legacy app being migrated looks nothing like a greenfield Rails 8 app. Loading every skill in the pack into context wastes tokens and confuses the agent. This skill narrows the context to what matters.
Rails 8 defaults (authoritative as of Rails 8.0)
When the user says "Rails 8 defaults," they mean this stack — confirmed against the official Rails 8 launch post:
| Layer | Rails 8 default | Notes |
|---|---|---|
| Database | SQLite (in rails new); PostgreSQL is the standard production swap |
Pass --database=postgresql for greenfield prod apps |
| Job adapter | Solid Queue | DB-backed; needs FOR UPDATE SKIP LOCKED (PG 9.5+, MySQL 8+, MariaDB 10.6+); Rails 8 itself requires Ruby 3.2+ |
| Cache store | Solid Cache | DB-backed; FIFO eviction; encrypted via Active Record Encryption |
| Cable adapter | Solid Cable | DB-backed pubsub; replaces Redis as Action Cable backend |
| Asset pipeline | Propshaft | Replaces Sprockets; only does load-path + digest stamping |
| JS bundling | Importmap | No Node toolchain by default |
| CSS | Plain CSS (--css=tailwind for Tailwind) |
|
| Front-end interactivity | Hotwire (Turbo + Stimulus) | Server-rendered HTML over the wire |
| Test framework | Minitest | The DHH/Rails-core default. We cover RSpec patterns in rspec-testing-pyramid for teams who prefer it; the pyramid shape transfers either way |
| Auth | Built-in bin/rails generate authentication (Rails 8.0+) |
Skip Devise for simple cases; use Devise/Rodauth for richer needs |
| Deploy | Kamal 2 + Thruster + Kamal Proxy | Container-first, zero-downtime via GET /up, Let's Encrypt SSL auto |
What ships with it
1 file 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.
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.
- 12d ago First seen · 260 lines · 158 tokens per session scan A d37a8ca833fb
rails-project-discovery is a skill published in the GitHub repository sandeepmvl/rails-skills (21 stars, last pushed 3mo ago), licensed MIT. It adds 158 tokens to every session and 4,604 once invoked, about $0.0008 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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