About OpenAPI Schema Generator

Generate OpenAPI schemas from JSON samples with automatic type inference and property detection. Part of the DevTools Surf developer suite. Browse more tools in the API / Config collection.

Use Cases

• Generate an OpenAPI schema from a JSON API response sample to bootstrap API documentation.
• Create request/response schemas for new endpoints before writing the implementation.
• Produce component schemas for reuse across multiple OpenAPI paths.
• Generate schemas from Postman collection response examples for migration to OpenAPI.

Tips

• Provide a representative JSON sample with all optional fields populated — the generator infers types from values, so missing fields produce loose schemas.
• Review the inferred required array carefully — the generator marks all present fields as required by default; remove fields that can be absent in real responses.
• Add pattern constraints for string fields like emails, dates, and IDs after generation — the auto-inferred schema won't include regex patterns.

Fun Facts

• The OpenAPI Specification (formerly Swagger) was created by Tony Tam in 2010 at Wordnik. It was donated to the Linux Foundation's OpenAPI Initiative in 2015 by SmartBear Software.
• OpenAPI 3.0, released in 2017, added support for callbacks, links, and multiple authentication schemes — features missing from Swagger 2.0 that made it unsuitable for modern API designs.
• Over 2,000 open-source tools are built on OpenAPI including code generators (openapi-generator supports 50+ languages), documentation tools (Swagger UI, Redoc), and test frameworks — making OpenAPI the most ecosystemic API description format.

FAQ

Does it generate OpenAPI 3.0 or 3.1 schemas?

3.1 by default (aligned with JSON Schema 2020-12). Toggle to 3.0 for tools that haven't added 3.1 support yet — most popular tooling (Swagger UI, Stoplight) now supports 3.1.

Can I generate from multiple samples?

Yes — provide multiple JSON samples representing different responses (success, error, empty list) and the generator unions the schemas, marking fields as optional if they don't appear in all samples.

Does it infer string formats?

Yes — strings matching ISO 8601 dates are typed as 'format: date-time', UUID patterns as 'format: uuid', and email patterns as 'format: email'. Custom format detection can be added via regex rules.