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 rules/girijashankarj/cursor-handbook/api-designgit clone --depth 1 https://github.com/girijashankarj/cursor-handbookWrote 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/rules/girijashankarj/cursor-handbook/api-design)<a href="https://agentmods.dev/rules/girijashankarj/cursor-handbook/api-design"><img src="https://agentmods.dev/badge/rules/girijashankarj/cursor-handbook/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 | $0.00000 | $0.00775 |
| Opus 5 | $0.00000 | $0.00387 |
| Sonnet 5 | $0.00000 | $0.00155 |
| Haiku 4.5 | $0.00000 | $0.00077 |
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 — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Rules
URL Structure
/api/v{version}/{resource} # Collection
/api/v{version}/{resource}/{id} # Single resource
/api/v{version}/{resource}/{id}/{sub-resource} # Sub-resource
HTTP Methods
| Method | Action | Response Code | Idempotent |
|---|---|---|---|
| GET | Read | 200 | Yes |
| POST | Create | 201 | No |
| PUT | Full update | 200 | Yes |
| PATCH | Partial update | 200 | Yes |
| DELETE | Soft delete | 200 | Yes |
Response Envelope
{
"data": {},
"meta": {
"correlationId": "abc-123",
"timestamp": "2026-01-15T10:30:00Z",
"pagination": {
"page": 1,
"pageSize": 20,
"total": 150,
"hasNextPage": true,
"cursor": "eyJpZCI6MTIzfQ=="
}
}
}
Versioning
- Use URL path versioning:
/api/v1/,/api/v2/ - Support at most 2 active versions simultaneously
- Deprecation notice 6 months before version removal
- Document breaking changes in changelog
Query Parameters
| Parameter | Purpose | Example |
|---|---|---|
page, pageSize |
Pagination | ?page=2&pageSize=20 |
cursor |
Cursor pagination | ?cursor=abc123 |
sort |
Sorting | ?sort=-created_at,name |
filter |
Filtering | ?filter[status]=active |
fields |
Field selection | ?fields=id,name,email |
include |
Related resources | ?include=items,customer |
Rate Limiting
- Include rate limit headers in all responses:
X-RateLimit-Limit: Max requests per windowX-RateLimit-Remaining: Remaining requestsX-RateLimit-Reset: Window reset timestamp
- Return 429 when limit exceeded with
Retry-Afterheader
Anti-patterns
- Don't use 200 for errors — use 4xx/5xx with error body
- Don't nest resources > 2 levels —
/api/v1/orders/123/itemsOK; deeper = split - Don't return array without pagination — always paginate list endpoints
- Don't use query params for sensitive data — use headers or body
- Don't version in headers only — use URL path for cacheability
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 · 90 lines · 0 tokens per session scan A c3b073466d9f
api-design is a cursor rule published in the GitHub repository girijashankarj/cursor-handbook (30 stars, last pushed 3d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 775 tokens. 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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