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 roedyrustam/vibes-plug --skill api-design-expertgit clone --depth 1 https://github.com/roedyrustam/vibes-plugWrote 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/roedyrustam/vibes-plug/api-design-expert)<a href="https://agentmods.dev/skills/roedyrustam/vibes-plug/api-design-expert"><img src="https://agentmods.dev/badge/skills/roedyrustam/vibes-plug/api-design-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 | $0.00082 | $0.02673 |
| Opus 5 | $0.00041 | $0.01337 |
| Sonnet 5 | $0.00016 | $0.00535 |
| Haiku 4.5 | $0.00008 | $0.00267 |
Grade A, and why
api-design-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 7d 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 — 318 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Expert
English
Description
Expert guide for designing, documenting, and evolving production-grade APIs. Covers REST resource modeling and HTTP semantics, GraphQL schema design, gRPC with protobuf, and tRPC for end-to-end type-safe APIs in TypeScript monorepos. Includes OpenAPI 3.1 documentation, API versioning strategies, rate limiting, idempotency, and contract-first development workflows.
Trigger Conditions
- Designing a new API from scratch (REST, GraphQL, gRPC, or tRPC).
- Evolving an existing API without breaking clients.
- Documenting APIs with OpenAPI/Swagger.
- Implementing rate limiting, throttling, or idempotency.
- Choosing between REST, GraphQL, gRPC, and tRPC.
- Designing webhook systems.
- Implementing API authentication (API keys, JWT, OAuth2).
API Protocol Selection Guide
| Criteria | REST | GraphQL | gRPC | tRPC |
|---|---|---|---|---|
| Type Safety | Manual (OpenAPI) | Schema-enforced | Protobuf | End-to-end TS |
| Performance | Good | Good | Excellent (HTTP/2) | Good |
| Browser Support | Native | Native | Needs proxy | TS/JS only |
| Streaming | SSE / WebSocket | Subscriptions | Native bi-directional | SSE |
| Best For | Public APIs, mobile | Complex data graphs | Microservice-to-service | Next.js full-stack |
| Tooling | Universal | Rich ecosystem | Strong (Go, Java) | Next.js / Expo |
REST API Design Principles
Resource Naming Conventions
Collection: GET /api/v1/posts
Item: GET /api/v1/posts/{id}
Sub-resource:GET /api/v1/posts/{id}/comments
Action: POST /api/v1/posts/{id}/publish (use sparingly)
AVOID: /api/v1/getPosts, /api/v1/createPost, /api/v1/deletePost/{id}
HTTP Method Semantics
| Method | Idempotent | Safe | Use Case |
|---|---|---|---|
GET |
Yes | Yes | Retrieve resources |
POST |
No | No | Create resources, trigger actions |
PUT |
Yes | No | Replace entire resource |
PATCH |
No | No | Partial update |
DELETE |
Yes | No | Remove resource |
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.
- 7d ago First seen · 318 lines · 82 tokens per session scan A a45eaef9bc46
api-design-expert is a skill published in the GitHub repository roedyrustam/vibes-plug (49 stars, last pushed 3d ago), licensed MIT. It adds 82 tokens to every session and 2,673 once invoked, about $0.0004 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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