API Documentation with OpenAPI and Swagger

Good API documentation is the difference between developers loving or abandoning your API. OpenAPI provides a standard way to describe REST APIs.

OpenAPI Specification Basics#

Defining Endpoints#

Defining Schemas#

Reusable Components#

Express with Swagger UI#

Auto-Generate from Code#

Code Generation#

Validation with OpenAPI#

Best Practices#

Conclusion#

OpenAPI documentation serves as a contract between API providers and consumers. Invest in good documentation—it reduces support burden and improves developer adoption.

Generate docs from code when possible, validate requests against the spec, and keep documentation in sync with implementation.