Generate and maintain OpenAPI 3.1 specifications from code, design-first specs, and validation patterns. Use when creating API documentation, generating SDKs, or ensuring API contract compliance.

OpenAPI Spec Generation Comprehensive patterns for creating, maintaining, and validating OpenAPI 3.1 specifications for RESTful APIs. When to Use This Skill Creating API documentation from scratch Generating OpenAPI specs from existing code Designing API contracts (design first approach) Validating API implementations against specs Generating client SDKs from specs Setting up API documentation portals Core Concepts 1. OpenAPI 3.1 Structure 2. Design Approaches Approach Description Best For Design First Write spec before code New APIs, contracts Code First Generate spec from code Existing APIs Hybrid Annotate code, generate spec Evolving APIs Templates and detailed worked examples Full template library and detailed worked examples live in references/details.md . Read that file when you need the concrete templates. Best Practices Do's Use $ref Reuse schemas, parameters, responses Add examples Real world values help consumers Document errors All possible error codes Version your API In URL or header Use semantic versioning For spec changes Don'ts Don't use generic descriptions Be specific Don't skip security Define all schemes Don't forget nullable Be explicit about null Don't mix styles Consistent naming throughout Don't hardcode URLs Use server variables

openapi-spec-generation