api-and-interface-design
Helps design stable, well-documented APIs and interfaces with consistent contracts, error handling, validation at boundaries, and backward-compatible evolution.
What it does
Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.
Quality judgment
Exceptionally thorough coverage of API design: Hyrum's Law, one-version rule, error semantics, boundary validation, idempotency (with race conditions, retention, in-flight duplicates), REST patterns, TypeScript patterns, rationalizations table, red flags, and a verification checklist. Code examples are concrete and show both good and bad patterns; the idempotency section is unusually deep and correct. Triggers are clear but could better distinguish when NOT to use the skill.