What is an API definition?

An API definition is a standardized description of an API's structure and functionality, detailing endpoints, operations, data formats, authentication, and rate limiting, crucial for facilitating developer onboarding, collaboration, and governance. It supports testing, monitoring, scalability, and stability by providing a clear framework for API interaction. API definitions are machine-readable and can be used in CI/CD pipelines and to configure API gateways, which manage access and provide security features. Common formats for defining APIs include OpenAPI, GraphQL SDL, WSDL, gRPC, AsyncAPI, and Postman collections, each offering tools for documentation and interaction. These definitions serve as blueprints to streamline workflows, enhance reliability, and ensure scalability, with the choice of format depending on project requirements and technology stack.