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 fabioc-aloha/Alex_Skill_Mall --skill api-designgit clone --depth 1 https://github.com/fabioc-aloha/Alex_Skill_MallWrote 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/fabioc-aloha/alex_skill_mall/api-design)<a href="https://agentmods.dev/skills/fabioc-aloha/alex_skill_mall/api-design"><img src="https://agentmods.dev/badge/skills/fabioc-aloha/alex_skill_mall/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/fabioc-aloha/alex_skill_mall/api-design"><img src="https://agentmods.dev/badge/skills/fabioc-aloha/alex_skill_mall/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 | $0.00011 | $0.01406 |
| Opus 5 | $0.00005 | $0.00703 |
| Sonnet 5 | $0.00002 | $0.00281 |
| Haiku 4.5 | $0.00001 | $0.00141 |
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 8d 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 — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Skill
Design APIs that developers love to use.
Core Principle
A good API is intuitive, consistent, and hard to misuse. Design for the consumer, not the implementation.
REST Fundamentals
Resource Naming
| Good | Bad | Why |
|---|---|---|
/users |
/getUsers |
Nouns, not verbs |
/users/123 |
/user?id=123 |
Path params for identity |
/users/123/orders |
/getUserOrders |
Hierarchical resources |
/search?q=term |
/search/term |
Query params for filters |
HTTP Methods
| Method | Purpose | Idempotent | Safe |
|---|---|---|---|
| GET | Read resource | Yes | Yes |
| POST | Create resource | No | No |
| PUT | Replace resource | Yes | No |
| PATCH | Partial update | No* | No |
| DELETE | Remove resource | Yes | No |
Status Codes
| Code | Meaning | When to Use |
|---|---|---|
| 200 | OK | Successful GET, PUT, PATCH |
| 201 | Created | Successful POST |
| 204 | No Content | Successful DELETE |
| 400 | Bad Request | Validation error |
| 401 | Unauthorized | Missing authentication |
| 403 | Forbidden | Authenticated but not allowed |
| 404 | Not Found | Resource doesn't exist |
| 409 | Conflict | State conflict (duplicate) |
| 429 | Too Many Requests | Rate limited |
| 500 | Internal Error | Server bug |
Contract-First Design
- Define the contract (OpenAPI/Swagger)
- Review with consumers before coding
- Generate server stubs from contract
- Implement business logic
- Validate responses against contract
openapi: 3.1.0 # 3.1.0 aligns with JSON Schema 2020-12
info:
title: My API
version: 1.0.0
paths:
/users:
get:
summary: List users
responses:
'200':
description: Success
content:
application/json:
schema:
$ref: '#/components/schemas/UserList'
Versioning
| Strategy | Example | Recommendation |
|---|---|---|
| URL Path | /v1/users |
Preferred - explicit |
| Header | Accept: vnd.api.v1+json |
Clean but hidden |
| Query | /users?version=1 |
Avoid |
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.
- 8d ago First seen · 229 lines · 11 tokens per session scan A ba4e93014eea
api-design is a skill published in the GitHub repository fabioc-aloha/Alex_Skill_Mall (4 stars, last pushed today), licensed MIT. It adds 11 tokens to every session and 1,406 once invoked, about $0.0001 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 2026-09-03.
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