JSON Schema : JSON Schema is a vocabulary that allows you to annotate and validate JSON documents.
XgeneCloud : XgeneCloud is an API Framework platform that instantly generates REST / GraphQL APIs on any SQL database.
Supports MySQL, PostgreSQL, MSSQL, SQLite &...
Freebase : A community-curated database of well-known people, places, and things
Mockoon : Mockoon is the easiest and quickest way to design and run mock APIs. No remote deployment, no account required, free and open-source.
Webhook Tester : Webhook Tester allows you to easily test webhooks and other types of HTTP requests.
Bluepine is a DSL for defining API Schema/Endpoint with the capabilities to generate Open API (v3) spec, validate API request and serialize object for API response based on single schema definition.