agentmods.dev

api-patterns

A guide to designing web APIs, which are interfaces that let software systems communicate. It covers REST, GraphQL, and tRPC, plus response formats, versioning, pagination, authentication, rate limits, documentation, and security testing.

In plain words
What is it for?
Planning API structure, choosing between REST, GraphQL, and tRPC, designing responses and pagination, evolving an API, and planning its security and documentation.
Why use it?
It helps you choose an API style and make consistent decisions instead of assembling rules piecemeal.

Skill for Claude CodeCodex

8.2k yesterday A scan 28 tokens original MIT
View the source file vudovn/ag-kit
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/vudovn/ag-kit/api-patterns
Any agent
npx skills add vudovn/ag-kit --skill api-patterns
Clone the repo
git clone --depth 1 https://github.com/vudovn/ag-kit

Made for: Claude Code, Codex.

Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 625 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 $0.00028 $0.00625
Opus 5 $0.00014 $0.00313
Sonnet 5 $0.00006 $0.00125
Haiku 4.5 $0.00003 $0.00063

Measured yesterday against content hash b9f16c4cb87d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-patterns 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 yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/api_validator.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.

Origin

Copies of this mod

8 near-identical copies found in the catalogue:

.agents/skills/api-patterns/SKILL.md · 84 lines

How it starts

The opening of the file, as written. The whole thing — 84 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Patterns

API design principles and decision-making. Learn to THINK, not copy fixed patterns.

🎯 Selective Reading Rule

Read ONLY files relevant to the request! Check the content map, find what you need.

📑 Content Map

File Description When to Read
api-style.md REST vs GraphQL vs tRPC decision tree Choosing API type
rest.md Resource naming, HTTP methods, status codes Designing REST API
response.md Envelope pattern, error format, pagination Response structure
graphql.md Schema design, when to use, security Considering GraphQL
trpc.md TypeScript monorepo, type safety TS fullstack projects
versioning.md URI/Header/Query versioning API evolution planning
auth.md JWT, OAuth, Passkey, API Keys Auth pattern selection
rate-limiting.md Token bucket, sliding window API protection
documentation.md OpenAPI/Swagger best practices Documentation
security-testing.md OWASP API Top 10, auth/authz testing Security audits
Need Skill
API implementation @[skills/nodejs-best-practices]
Data structure @[skills/database-design]
Security details @[skills/vulnerability-scanner]

✅ Decision Checklist

Before designing an API:

  • Asked user about API consumers?
  • Chosen API style for THIS context? (REST/GraphQL/tRPC)
  • Defined consistent response format?
  • Planned versioning strategy?
  • Considered authentication needs?
  • Planned rate limiting?
  • Documentation approach defined?

❌ Anti-Patterns

DON'T:

  • Default to REST for everything
  • Use verbs in REST endpoints (/getUsers)
  • Return inconsistent response formats
  • Expose internal errors to clients
  • Skip rate limiting

DO:

  • Choose API style based on context
  • Ask about client requirements
  • Document thoroughly
  • Use appropriate status codes

Read the full file on GitHub · 84 lines

Files

What ships with it

11 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. yesterday First seen · 84 lines · 28 tokens per session scan A b9f16c4cb87d

Subscribe to this mod's changes

api-patterns is a skill published in the GitHub repository vudovn/ag-kit (8,160 stars, last pushed yesterday), licensed MIT. It adds 28 tokens to every session and 625 once invoked, about $0.0001 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 APIsSecurityTesting
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