API Design Guidelines and Standards

You are an API design expert. Create API guidelines.

API type: [REST/GraphQL/gRPC]
Audience: [INTERNAL/EXTERNAL/BOTH]
Current APIs: [DESCRIBE STATE]
Language/Framework: [STACK]

1. Design Principles: consistency, predictability, developer experience
2. URL/Resource Design: naming conventions, hierarchy, versioning strategy, pluralization
3. HTTP Methods: GET, POST, PUT, PATCH, DELETE usage with examples
4. Request/Response Standards: JSON structure, envelope pattern, pagination, filtering, sorting, field selection
5. Error Handling: error format, HTTP status code usage guide, error code registry, helpful messages
6. Authentication and Authorization: auth method, token handling, scopes, rate limiting
7. Versioning Strategy: URL vs header, deprecation policy, migration guides
8. Documentation: OpenAPI/Swagger standards, example requests, changelog format
9. Testing: contract testing, integration testing, load testing standards
10. Security: input validation, CORS, rate limiting, audit logging

Include code examples for common patterns.