Backend APIs: HTTP Service Design and Implementation

Design and review HTTP APIs that stay coherent as they grow. Focus on contracts, auth boundaries, error models, and framework structure for Python and Node.js services.

Target versions: see references/versions.md (verified per the receipt date in that file). Do not restate version numbers here.

This skill works across these concerns:

• Contract design - resources, methods, status codes, schemas, versioning
• API ergonomics - pagination, filtering, sorting, idempotency, error format
• Framework structure - FastAPI dependencies, Express middleware, NestJS modules and guards
• Authentication - sessions, bearer tokens, OAuth/OIDC, BFF and token mediation
• Review - unstable contracts, DTO leakage, auth confusion, and HTTP misuse
• Bounded protocol patterns - GraphQL schema/resolver and gRPC contract, deadline, retry, and streaming safeguards when those protocols are already in scope

When to use