The Swagger API explorer is the easiest way to learn the API. Swagger is a tool that shows what parameters and options the API accepts and how it responds to your requests. Swagger also acts as live documentation that is always up-to-date with the Magnolia instance it runs on. Swagger API Explorer supports both XML and JSON in the request body but it returns only JSON. You can find the tool in Dev > REST Tools when the REST Tools module is installed.