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/hoavdc/codexkit/codexkit-api-design-reviewernpx skills add hoavdc/CodexKit --skill codexkit-api-design-reviewergit clone --depth 1 https://github.com/hoavdc/CodexKitWhat 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 | $0.00060 | $0.01382 |
| Opus 5 | $0.00030 | $0.00691 |
| Sonnet 5 | $0.00012 | $0.00276 |
| Haiku 4.5 | $0.00006 | $0.00138 |
Grade A, and why
codexkit-api-design-reviewer 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 2d 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 — 167 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Reviewer
When to Use
- When reviewing an OpenAPI/Swagger specification before implementation
- When auditing existing API endpoints for consistency
- When designing a new API from scratch
- When preparing APIs for external/partner consumption
Procedure
Step 1 — Naming & Convention Check
| Check | Rule | Example |
|---|---|---|
| Resource naming | Plural nouns, kebab-case | ✅ /api/v1/order-items ❌ /api/v1/getOrderItem |
| HTTP methods | GET=read, POST=create, PUT=replace, PATCH=partial, DELETE=remove | ✅ POST /orders ❌ POST /create-order |
| Query params | camelCase for filters/sorting | ✅ ?sortBy=createdAt ❌ ?sort_by=created_at |
| Status codes | Use standard codes correctly | ✅ 201 Created, 204 No Content ❌ 200 for everything |
| Consistency | Same pattern across all endpoints | Check all resources follow same naming |
Step 2 — Versioning Strategy
| Strategy | When to Use | Pattern |
|---|---|---|
| URL path | Simple, widely adopted | /api/v1/orders |
| Header | Cleaner URLs, harder to test | Accept: application/vnd.api+json;version=1 |
| Query param | Easy to test, but less RESTful | /api/orders?version=1 |
Verify:
- Version is present in all endpoints
- Deprecation policy documented
- Migration guide for version bumps
Step 3 — Error Format
Errors should follow a consistent structure:
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Human-readable description",
"details": [
{
"field": "email",
"issue": "Invalid format",
"expected": "Valid email address"
}
],
"request_id": "req_abc123",
"docs_url": "https://docs.api.com/errors/VALIDATION_ERROR"
}
}
Check:
- Error format consistent across all endpoints
- Machine-readable error codes (not just messages)
- Request ID for traceability
- No sensitive data in error responses
Step 4 — Pagination
| Pattern | Best For | Implementation |
|---|---|---|
| Cursor-based | Large datasets, real-time data | ?cursor=abc&limit=20 |
| Offset-based | Simple lists, admin UIs | ?page=2&per_page=20 |
| Keyset | Time-series data | ?after=2024-03-15T00:00:00Z&limit=20 |
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 167 lines · 60 tokens per session scan A c5e9a683a875
codexkit-api-design-reviewer is a skill published in the GitHub repository hoavdc/CodexKit (21 stars, last pushed 3mo ago), licensed MIT. It adds 60 tokens to every session and 1,382 once invoked, about $0.0003 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 2026-08-30.
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