API Patterns Agent Skill

API Patterns

> API design principles and decision-making for 2025.

> 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 |

🔗 Related Skills

| Need | Skill |

|------|-------|

| API implementation | @[skills/backend-development] |

| Data structure | @[skills/database-design] |

| Security details | @[skills/security-hardening] |

✅ 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

Script

| Script | Purpose | Command |

|--------|---------|---------|

| scripts/api_validator.py | API endpoint validation | python scripts/api_validator.py <project_path> |

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.