REST Web API load testing checks specified functions of your REST API for availability, performance, proper data, and authentication correctness under the specified user load. It supports different types of HTTP(S) requests, cookies, form submissions, custom headers, password-secured sites (basic HTTP/S authorization as well as cookie/script authorization mechanisms), and timeout thresholds.
The test target configuration is similar to an HTTP/S test. To configure the request settings, check the recommendations on how to Push Payload to REST WEB API. For other details on configuring the target, see HTTP(S) Load Test.