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 jamestorrevillas/dev-skills --skill api-designgit clone --depth 1 https://github.com/jamestorrevillas/dev-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/jamestorrevillas/dev-skills/api-design)<a href="https://agentmods.dev/skills/jamestorrevillas/dev-skills/api-design"><img src="https://agentmods.dev/badge/skills/jamestorrevillas/dev-skills/api-design/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/jamestorrevillas/dev-skills/api-design"><img src="https://agentmods.dev/badge/skills/jamestorrevillas/dev-skills/api-design.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 | $0.00065 | $0.01026 |
| Opus 5.5 | $0.00026 | $0.00410 |
| Sonnet 5.5 | $0.00013 | $0.00205 |
| Haiku 4.5 | $0.00006 | $0.00103 |
Grade A, and why
api-design 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 1mo 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 — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design
Choosing the Right API Type
| Type | Best For | Avoid When |
|---|---|---|
| REST | Public APIs, CRUD, simple clients, IoT | Complex nested data, rapid schema iteration |
| GraphQL | Mobile apps, complex nested data, multiple clients | Simple CRUD, small teams new to it |
| tRPC | TypeScript monorepos, internal full-stack TS APIs | Non-TypeScript clients, public APIs |
| gRPC | High-performance microservice comms, streaming | Browser clients, simple use cases |
REST API Design
URL Conventions
GET /users ← list
GET /users/{id} ← single
POST /users ← create
PUT /users/{id} ← replace
PATCH /users/{id} ← partial update
DELETE /users/{id} ← delete
# Nested resources
GET /users/{id}/orders
POST /users/{id}/orders
# Actions (when REST verbs aren't enough)
POST /orders/{id}/cancel
POST /users/{id}/activate
HTTP Status Codes
| Code | Use When |
|---|---|
| 200 | Successful GET, PUT, PATCH |
| 201 | Successful POST that creates |
| 204 | Successful DELETE (no body) |
| 400 | Validation failure, bad request |
| 401 | Missing/invalid authentication |
| 403 | Authenticated but not authorized |
| 404 | Resource not found |
| 409 | Conflict (duplicate, version mismatch) |
| 422 | Unprocessable entity (semantic errors) |
| 429 | Rate limit exceeded |
| 500 | Unexpected server error |
Response Envelope
// Collection
{
"data": [...],
"meta": { "total": 100, "page": 1, "perPage": 20 }
}
// Single resource
{ "data": { "id": "1", "name": "James" } }
// Error
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Validation failed",
"details": [{ "field": "email", "issue": "Invalid format" }]
}
}
API Design Principles
Versioning Strategy
# URL versioning (most visible, easiest to route)
/v1/users
/v2/users
# Header versioning (cleaner URLs)
Accept: application/vnd.api+json;version=2
```text
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.
- 1mo ago First seen · 154 lines · 0 tokens per session scan A abb6b4033f94
api-design is a skill published in the GitHub repository jamestorrevillas/dev-skills (3 stars, last pushed 7mo ago), licensed MIT. It adds 65 tokens to every session and 1,026 once invoked, about $0.0003 per session on Opus 5.5. 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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