OpenAPI Specification v2.0 – formerly known as Swagger RESTful API Documentation Specification.
Swagger™ is a project used to describe and document RESTful APIs.
The Swagger specification defines a set of files required to describe such an API. These files can then be used by the Swagger-UI project to display the API and Swagger-Codegen to generate clients in various languages. Additional utilities can also take advantage of the resulting files, such as testing tools.