API and Interface Design

Contract-first design for HTTP APIs, GraphQL, CLI surfaces, and library module boundaries. Complements secure-api-design (security) and agent-tool-contracts (LLM tools) with general interface ergonomics and evolution rules.

When to use

• New public or cross-team API
• Breaking-change review
• Designing pagination, filtering, idempotency, or error shapes

When not to use

• Internal refactor with no boundary change
• Security-only audit (use secure-api-design)
• Agent tool schema only (use agent-tool-contracts)

Design checklist

Contract