If your web API (HTTP trigger) is being used by multiple client applications and you would like to provide access only to the intended and authorized applications, then you need to implement authorization in order to restrict access to your Azure Function.
Enabling authorization for function apps
Getting ready
I assume that you already know how to create a HTTP trigger function. Download the Postman tool from https://www.getpostman.com/. The Postman tool is used for sending the HTTP requests. You can also use any tool or application that can send HTTP requests and headers.
