api-design

A guide for designing and reviewing HTTP APIs, which are the rules software uses to communicate over the web. It covers REST-style resources, input checks, response formats, errors, versioning, and OpenAPI documentation.

In plain words
What is it for?
Use it when adding or changing auth-server routes, defining request or response schemas, choosing status codes, or reviewing API contracts.
Why use it?
It keeps endpoints predictable and helps prevent clients from receiving inconsistent data or error messages.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/qauth-labs/qauth/api-design
Any agent
npx skills add qauth-labs/qauth --skill api-design
Clone the repo
git clone --depth 1 https://github.com/qauth-labs/qauth

Made for: Claude Code, Codex.

Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,348 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00052 $0.01348
Opus 5 $0.00026 $0.00674
Sonnet 5 $0.00010 $0.00270
Haiku 4.5 $0.00005 $0.00135

Measured 3d ago against content hash 4a953bfeab38, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 3d 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.

.claude/skills/api-design/SKILL.md · 100 lines

How it starts

The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Design (QAuth)

Standards-aligned HTTP API design for QAuth auth-server. APIs are resource-oriented, schema-validated with Zod, and return consistent success and error payloads. Use this skill when defining new endpoints, schemas, or reviewing API contracts.

When to Use This Skill

  • Adding or changing routes in apps/auth-server
  • Defining or updating request/response schemas (Zod)
  • Designing error response shape or status codes
  • Questions about REST conventions, versioning, or OpenAPI

Quick Reference

Concern QAuth pattern
Validation Zod schemas in app/schemas/; fastify-type-provider-zod on routes
Route schema schema: { body?, querystring?, params?, response: { 200: schema } }
Success 200/201/204 with typed body; no extra envelope unless needed
Errors { error, statusCode, code?, feedback?, constraint?, retryAfter?, details? }
OAuth tokens RFC 6749: snake_case (access_token, refresh_token, expires_in, token_type)
Other JSON camelCase for app-specific fields (e.g. emailVerified, realmId)
Versioning Not in use yet; prefer path /v1/ or header when introduced

Route Structure (QAuth)

  1. Schemas first
    Define Zod schemas in app/schemas/ (e.g. auth.ts, oauth.ts, common.ts). Export schema and inferred type (z.infer<typeof schema>). Use z.email(), z.uuid(), z.url() (Zod v4 standalone validators).

  2. Register schema on route
    Use fastify.withTypeProvider<ZodTypeProvider>().get|post|...(path, { schema, config }, handler). Set schema.body, schema.querystring, schema.params, and schema.response (e.g. response: { 200: responseSchema }). Fastify validates and types request/response.

Read the full file on GitHub · 100 lines

Files

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.

Changes

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.

  1. 3d ago First seen · 100 lines · 52 tokens per session scan A 4a953bfeab38

Subscribe to this mod's changes

api-design is a skill published in the GitHub repository qauth-labs/qauth (24 stars, last pushed 7d ago), licensed Apache-2.0. It adds 52 tokens to every session and 1,348 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.