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 MadAppGang/claude-code --skill api-designgit clone --depth 1 https://github.com/MadAppGang/claude-codeWrote 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/madappgang/claude-code/api-design)<a href="https://agentmods.dev/skills/madappgang/claude-code/api-design"><img src="https://agentmods.dev/badge/skills/madappgang/claude-code/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/madappgang/claude-code/api-design"><img src="https://agentmods.dev/badge/skills/madappgang/claude-code/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 | $0.00035 | $0.01887 |
| Opus 5.5 | $0.00014 | $0.00755 |
| Sonnet 5.5 | $0.00007 | $0.00377 |
| Haiku 4.5 | $0.00003 | $0.00189 |
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 — 386 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Patterns
Overview
RESTful and GraphQL API design patterns for building robust backend services.
REST API Design
Resource Naming
| Pattern | Example | Description |
|---|---|---|
| Plural nouns | /users, /orders |
Collections |
| Nested resources | /users/{id}/orders |
Sub-resources |
| No verbs in URLs | /users not /getUsers |
Actions via HTTP methods |
| Lowercase, hyphens | /order-items |
Consistent casing |
HTTP Methods
| Method | Purpose | Idempotent | Example |
|---|---|---|---|
| GET | Read | Yes | GET /users/123 |
| POST | Create | No | POST /users |
| PUT | Replace | Yes | PUT /users/123 |
| PATCH | Update | Yes | PATCH /users/123 |
| DELETE | Remove | Yes | DELETE /users/123 |
Status Codes
| Code | Meaning | Usage |
|---|---|---|
| 200 | OK | Successful GET/PUT/PATCH |
| 201 | Created | Successful POST |
| 204 | No Content | Successful DELETE |
| 400 | Bad Request | Validation error |
| 401 | Unauthorized | Missing/invalid auth |
| 403 | Forbidden | Insufficient permissions |
| 404 | Not Found | Resource doesn't exist |
| 409 | Conflict | Duplicate/conflict |
| 422 | Unprocessable | Semantic error |
| 500 | Server Error | Unexpected error |
Request/Response Format
// Successful response
{
"data": {
"id": "123",
"name": "John Doe",
"email": "[email protected]"
},
"meta": {
"requestId": "req_abc123"
}
}
// Error response
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Invalid email format",
"details": [
{
"field": "email",
"message": "Must be a valid email address"
}
]
},
"meta": {
"requestId": "req_abc123"
}
}
// List response
{
"data": [
{ "id": "1", "name": "User 1" },
{ "id": "2", "name": "User 2" }
],
"pagination": {
"total": 100,
"page": 1,
"pageSize": 20,
"totalPages": 5
}
}
Pagination
Offset Pagination
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 · 386 lines · 35 tokens per session scan A a692736ffe59
api-design is a skill published in the GitHub repository MadAppGang/claude-code (286 stars, last pushed 7mo ago), licensed MIT. It adds 35 tokens to every session and 1,887 once invoked, about $0.0001 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 2026-09-03.
Other skills, from other repositories
api-design
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Turn any OpenAPI, Swagger, or OpenRPC API into CLI commands and call them. Search endpoints with BM25, check parameters, execute — no MCP server needed.
openapi-expert
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api-designer
Designs production-grade APIs — REST, GraphQL, gRPC, and AsyncAPI patterns including pagination, versioning, error handling, rate limiting, and API governance. Use when the user asks to design APIs, create endpoints, build an API layer, write OpenAPI specs, or needs help with REST/GraphQL/gRPC service design.