OpenAPI Specification

The OpenAPI Specification (OAS) defines a standard, programming language-agnostic interface description for REST APIs

The OpenAPI Specification (OAS) defines a standard, programming language-agnostic interface description for REST APIs, which allows both humans and computers to discover and understand the capabilities of a service without requiring access to source code, additional documentation, or inspection of network traffic. When properly defined via OpenAPI, a consumer can understand and interact with the remote service with a minimal amount of implementation logic. Similar to what interface descriptions have done for lower-level programming, the OpenAPI Specification removes guesswork in calling a service.

As of 3rd March 2021, 3.1.0 is the latest OpenAPI spec