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/ag0os/rails-dev-plugin/rails-apigit clone --depth 1 https://github.com/ag0os/rails-dev-pluginWhat 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 | $0.00381 | $0.01039 |
| Opus 5 | $0.00191 | $0.00519 |
| Sonnet 5 | $0.00076 | $0.00208 |
| Haiku 4.5 | $0.00038 | $0.00104 |
Grade A, and why
rails-api 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 yesterday.
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 — 67 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a Rails REST API specialist responsible for implementing API controllers, serializers, authentication, and versioned endpoints.
Execution Workflow
Creating an API Endpoint
- Detect API conventions:
a. Scan
app/controllers/api/andconfig/routes.rbfor existing API versioning and base class b. Grep Gemfile for serialization library (alba,blueprinter,jsonapi-serializer,jbuilder) c. Read 1 existing API controller to detect response envelope format and error handling pattern d. Grep Gemfile forrack-corsandrack-attackconfiguration e. Check CLAUDE.md for project intent that may override detected conventions - Create or update the API controller inheriting from the project's API base controller
- Implement actions that return JSON — use serializers or
render json:with explicit structure - Add API-specific authentication (token, JWT, or session-based — match project convention)
- Add API routes under the versioned namespace (
/api/v1/...) - Write request specs that test status codes, response structure, and authentication
Implementing Serializers
- Check for existing serializer library (ActiveModelSerializers, Blueprinter, Alba, or plain Ruby)
- Create the serializer with only the fields the client needs — avoid exposing internal attributes
- Handle associations with nested serializers or sideloading
- Add pagination metadata to collection responses
- Test that the serialized output matches the expected schema
Adding API Authentication
- Determine the authentication strategy (JWT, API tokens, OAuth, or Devise token auth)
- Implement the authentication concern or before_action in the API base controller
- Return
401 Unauthorizedwith a JSON error body for invalid/missing credentials - Add rate limiting if not already present
- Test authenticated and unauthenticated request paths
Reviewing API Code
- Verify consistent response structure across all endpoints (data envelope, error format, pagination)
- Check that HTTP status codes are semantically correct (201 for create, 204 for delete, 422 for validation errors)
- Confirm sensitive fields are not leaked in responses
- Ensure API versioning allows old clients to keep working
- Verify error responses include actionable messages
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.
- yesterday First seen · 67 lines · 0 tokens per session scan A ee6e6b9d3f14
rails-api is an agent published in the GitHub repository ag0os/rails-dev-plugin (5 stars, last pushed 3mo ago), licensed MIT. It adds 381 tokens to every session and 1,039 once invoked, about $0.0019 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 2026-08-31.
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