Hello, can you clarify which API you are trying to access or what you are trying to achieve? You only need an API key if your app or service needs to access the Webex API as an anonymous user, then you need to pre-register an API key and then use HM256 algorithm to generate JWT token to access Webex anonymous API.
I would also advice checking out the Rest API service as the XML service will soon be discontinued. Webex Rest APIs are documented here; https://developer.webex.com/docs/platform-introduction
