Using OpenAPI
The OpenAPI Specification (https://www.openapis.org/), previously known as Swagger, is a standard way of describing a set of HTTP endpoints, how they are used, and the structure of the data that is sent and received. By describing an API using a JSON or YAML file, it allows the intent to become machine-readable—this means that with an OpenAPI Specification, you can use a code generator to produce a client library in a language of your choosing, or to automatically validate data as it enters or leaves the system.
OpenAPI has the same goal that WSDL (https://www.w3.org/TR/2001/NOTE-wsdl-20010315) had back in the XML web services era, but it's much lighter and straight to the point.
The following example is a minimal OpenAPI description file that defines one single /apis/users_ids endpoint and supports the GET method to retrieve the list of user IDs:
---
openapi: "3.0.0"
info:
title: Data Service
description: returns info about users...