How was the specification for REST endpoints described? What is inside the document?

REST endpoints specifications are usually described in the OpenAPI (Swagger) format or in technical documentation, where for each endpoint the following are specified:

• HTTP method (GET, POST, PUT, DELETE, etc.)
• URL path with parameters
• Description of the endpoint's purpose
• Format and structure of incoming data (request body, query parameters, headers)
• Format and structure of responses (response body, status codes)
• Possible errors and their handling

The document may include examples of requests and responses, as well as descriptions of authorization and restrictions. This approach helps developers and testers understand how to interact with the API.