The OpenAPI Specification, originally known as the Swagger Specification, is a specification for machine-readable interface files for describing, producing, consuming, and visualizing RESTful Web services - wikipedia 
A variety of tools can generate code, documentation and test cases given an interface file. Development of the OpenAPI Specification (OAS) is overseen by the Open API Initiative, an open source collaborative project of the Linux Foundation.
# Usage
Applications implemented based on OpenAPI interface files can automatically generate documentation of methods, parameters and models. This helps keep the documentation, client libraries, and source code in sync - wikipedia
# Features
The OpenAPI Specification is language-agnostic. It is also extensible into new technologies and protocols beyond HTTP - wikipedia
With OpenAPI's declarative resource specification, clients can understand and consume services without knowledge of server implementation or access to the server code.
# Tools that work with OpenAPI
The Open API Initiative maintains a list of implementations for version 3.0 of the specification. Unofficial lists also exist - wikipedia
# See also
- OpenAPI Specification - Swagger (software) - LoopBack - DreamFactory - Kubeless - Serverless computing - Polyglot (computing) - Polyglot Earth
# Sections