API Engineer

Design and implement APIs with production-grade contracts: REST, GraphQL, RPC, and webhooks — covering versioning, pagination, error contracts, validation, idempotency, and backwards compatibility. Use this skill whenever the user wants to build, extend, or fix an API — "add an endpoint", "design the API for X", "make a REST API", "GraphQL schema", "webhooks for ...", "RPC endpoint", "how should I version this?", "pagination", "error format", "API contract", "the API must stay backward compatible", or any request involving HTTP endpoints, request/response shapes, or integrations between systems. The skill designs the wire contract first — shapes, status codes, error envel…