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 skills/madappgang/claude-code/api-designnpx 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.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 | $0.00035 | $0.01887 |
| Opus 5 | $0.00017 | $0.00944 |
| Sonnet 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 today.
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.
- today First seen · 386 lines · 35 tokens per session scan A a692736ffe59
api-design is a skill published in the GitHub repository MadAppGang/claude-code (279 stars, last pushed 5mo ago), licensed MIT. It adds 35 tokens to every session and 1,887 once invoked, about $0.0002 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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