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api-design

api-design is a skill for Claude Code, Codex from johnqtcg/awesome-skills. It costs 123 tokens per session (7,448 once invoked), scanned A, original, MIT.

A REST API design and review guide for defining how web services expose data and actions to other programs.

In plain words
What is it for?
Use it to design or review endpoints, resource URLs, error responses, filtering, sorting, idempotency, authentication, and compatibility.
Why use it?
It helps keep endpoint names, HTTP methods, status codes, errors, pagination, retries, and version changes predictable for API users.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

not rated 30repo yesterday A scan SkillSpector: pass 123 tokens original MIT

Good fit Use it to design or review endpoints, resource URLs, error responses, filtering, sorting, idempotency, authentication, and compatibility.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/johnqtcg/awesome-skills/api-design
View source ↗ johnqtcg/awesome-skills johnqtcg.github.io
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.

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

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for api-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/johnqtcg/awesome-skills/api-design/github.svg)](https://agentmods.dev/skills/johnqtcg/awesome-skills/api-design)
Your own site
<a href="https://agentmods.dev/skills/johnqtcg/awesome-skills/api-design"><img src="https://agentmods.dev/badge/skills/johnqtcg/awesome-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.

agentmods 80×15 button for api-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/johnqtcg/awesome-skills/api-design"><img src="https://agentmods.dev/badge/skills/johnqtcg/awesome-skills/api-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 123 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,448 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00123 $0.07448
Opus 5 $0.00062 $0.03724
Sonnet 5 $0.00025 $0.01490
Haiku 4.5 $0.00012 $0.00745

Measured 9d ago against content hash 0d4cc7cc0428, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, 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 9d ago.

The scan reads SKILL.md. This mod also ships 5 executable files (scripts/lint_api_doc.py, scripts/run_regression.sh, scripts/tests/test_doc_lint.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/api-design/SKILL.md · 475 lines

How it starts

The opening of the file, as written. The whole thing — 475 lines — stays where its author put it; the contents beside it link to each section on GitHub.

REST API Design Review

Quick Reference

If you need to… Go to
Understand what this skill covers §1 Scope
Know how binding each rule is §2 Rule Nature and Finding Severity
Check mandatory prerequisites §3 Mandatory Gates
Choose review depth §4 Depth Selection
Handle incomplete context §5 Degradation Modes
Evaluate API design item by item §6 Design Checklist
Avoid common API design mistakes §7 Anti-Examples
Score the review result §8 Scorecard
Format review output §9 Output Contract
Deep-dive error model patterns references/error-model-patterns.md
Check compatibility rules references/compatibility-rules.md

§1 Scope

In scope — REST API contract design and review:

  • Resource modeling (URL structure, naming, hierarchy)
  • HTTP method semantics (GET/POST/PUT/PATCH/DELETE)
  • Status code selection (2xx/4xx/5xx semantic correctness)
  • Error model design (machine-parseable codes, field-level details)
  • Pagination, filtering, sorting, search patterns
  • Idempotency (Idempotency-Key header, retry safety)
  • Concurrency control (ETag, If-Match, optimistic locking)
  • Auth/AuthZ per endpoint, IDOR prevention
  • Rate limiting (per-actor, 429 + Retry-After)
  • Versioning, backward compatibility, deprecation planning
  • OpenAPI/Swagger contract generation

Out of scope — delegate to dedicated skills:

  • API integration testing → api-integration-test
  • gRPC/Protobuf design → separate skill
  • Application code implementation → go-code-reviewer

Read the full file on GitHub · 475 lines

Files

What ships with it

31 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.

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. 9d ago First seen · 475 lines · 123 tokens per session scan A 0d4cc7cc0428

Subscribe to this mod's changes

api-design is a skill published in the GitHub repository johnqtcg/awesome-skills (30 stars, last pushed yesterday), licensed MIT. It adds 123 tokens to every session and 7,448 once invoked, about $0.0006 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.

Backend and APIsClaude Codeagentsai-assistantai-skillsanthropicdeveloper-tools
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