API Designer skill: what it does and how to install it

What it does. Analyses domain and client needs, models resources and relationships, then defines endpoints, schemas, authentication, errors, pagination and versioning. Produces a resource model, endpoint design and OpenAPI 3.1 specification with RFC 7807 error responses, examples and validation using npx @redocly/cli lint; contracts can be mocked with Prism.

When to use it. For REST or GraphQL API architecture, OpenAPI specifications, resource modelling, versioning, pagination and error-handling standards. It includes authentication, rate limiting and backward-compatibility considerations in the design.