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 event4u-app/agent-config --skill api-designgit clone --depth 1 https://github.com/event4u-app/agent-configWrote 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/event4u-app/agent-config/api-design)<a href="https://agentmods.dev/skills/event4u-app/agent-config/api-design"><img src="https://agentmods.dev/badge/skills/event4u-app/agent-config/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/event4u-app/agent-config/api-design"><img src="https://agentmods.dev/badge/skills/event4u-app/agent-config/api-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00040 | $0.01070 |
| Opus 5.5 | $0.00016 | $0.00428 |
| Sonnet 5.5 | $0.00008 | $0.00214 |
| Haiku 4.5 | $0.00004 | $0.00107 |
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 5d 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 — 123 lines — stays where its author put it; the contents beside it link to each section on GitHub.
api-design
Grounded corpus (Tier-1 consultation): pagination, versioning, error shape (RFC 9457), idempotency, async ops, rate limiting, bulk, naming, expansion, webhooks — query
node <skills-root>/corpus-grounding/scripts/ground.mjs search --manifest <skills-root>/api-design/data/manifest.json "<concern>"and propose the grounded pattern (+ hardening + anti-patterns + RFC link) before designing from memory. Corpus:data/api-patterns.csv.
When to use
Use this skill when designing new API endpoints, restructuring existing APIs, or deciding about versioning and deprecation.
Do NOT use when:
- Implementing an already-designed endpoint (use
api-endpointskill) - Writing tests for APIs (use
api-testingskill)
Procedure: Design an API
- Gather context — read
agents/settings/contexts/api-versioning.md,agents/reference/docs/api-resources.md,agents/reference/docs/query-filter.md,agents/reference/docs/controller.md, and guidelinephp/api-design.md. - Identify the resource — determine the domain entity, its attributes, and relationships. Check existing models and resources for field naming patterns.
- Define endpoints — list each endpoint with HTTP method, URL path, request body, query parameters, and response structure. Follow existing route file patterns.
- Decide versioning — determine whether this extends the current version or requires a new version (see decision table below).
- Design error responses — define 4xx/5xx responses matching the project's existing error format.
- Validate against existing patterns — compare your design with 2-3 similar existing endpoints. Flag any inconsistencies.
- Run adversarial review — use
adversarial-reviewskill to check for breaking changes, consistency issues, and missing error cases.
Versioning decisions
URL-based versioning
Routes versioned via URL prefix: /api/v1/..., /api/v2/...
routes/api/v1/projects.php → /api/v1/projects (Laravel)
app/api/v1/projects/route.ts → /api/v1/projects (Next.js)
routes/api/v2/projects.php → /api/v2/projects
What ships with it
3 files 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.
- 5d ago Changed 511c8158dd3e
- 1mo ago First seen · 123 lines · 40 tokens per session scan A c625fc79747c
api-design is a skill published in the GitHub repository event4u-app/agent-config (12 stars, last pushed yesterday), licensed MIT. It adds 40 tokens to every session and 1,070 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 2026-08-31.
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