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 kazdenc/builder-skills --skill api-designgit clone --depth 1 https://github.com/kazdenc/builder-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/kazdenc/builder-skills/api-design)<a href="https://agentmods.dev/skills/kazdenc/builder-skills/api-design"><img src="https://agentmods.dev/badge/skills/kazdenc/builder-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/kazdenc/builder-skills/api-design"><img src="https://agentmods.dev/badge/skills/kazdenc/builder-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 | $0.00054 | $0.02622 |
| Opus 5.5 | $0.00022 | $0.01049 |
| Sonnet 5.5 | $0.00011 | $0.00524 |
| Haiku 4.5 | $0.00005 | $0.00262 |
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 — 292 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design
Apply these conventions when designing, reviewing, or implementing RESTful APIs. Consistency matters more than cleverness — follow the patterns below.
URL Structure
Use nouns for resources, not verbs. Resources are things, not actions.
| Rule | Correct | Incorrect |
|---|---|---|
| Plural nouns | /users, /orders |
/user, /getOrders |
| Nouns, not verbs | POST /users |
POST /createUser |
| Kebab-case for multi-word | /line-items |
/lineItems, /line_items |
| Nest for relationships (max 2 levels) | /users/:id/orders |
/users/:id/orders/:orderId/items/:itemId |
| Flat when parent is obvious | /orders/:orderId/items |
/users/:userId/orders/:orderId/items |
Query Parameters
Use query parameters for filtering, sorting, searching, and pagination. Never encode these in the URL path.
GET /users?status=active&sort=-created_at&limit=20&cursor=abc123
GET /orders?user_id=42&min_total=100&fields=id,status,total
| Parameter | Convention | Example |
|---|---|---|
| Filter | Field name as key | ?status=active&role=admin |
| Sort | Field name, prefix - for descending |
?sort=-created_at,name |
| Search | q parameter |
?q=john |
| Field selection | fields comma-separated |
?fields=id,name,email |
| Pagination | cursor or offset/limit |
?cursor=abc&limit=20 |
HTTP Methods
| Method | Purpose | Idempotent | Request Body | Success Code | Response Body |
|---|---|---|---|---|---|
GET |
Retrieve resource(s) | Yes | No | 200 |
Resource or collection |
POST |
Create a new resource | No | Yes | 201 |
Created resource |
PUT |
Replace a resource entirely | Yes | Yes | 200 |
Updated resource |
PATCH |
Partially update a resource | No* | Yes | 200 |
Updated resource |
DELETE |
Remove a resource | Yes | No | 204 |
No body |
*PATCH is not inherently idempotent but can be implemented as such. Treat it as non-idempotent by default.
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 · 292 lines · 54 tokens per session scan A b2d2b7b22efc
api-design is a skill published in the GitHub repository kazdenc/builder-skills (46 stars, last pushed 7mo ago), licensed MIT. It adds 54 tokens to every session and 2,622 once invoked, about $0.0002 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 2026-08-30.
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