How to debug API calls from iOS apps with APItools (docs.apitools.com)

Do you need to register the APIs you use in APItools before doing this?

Isn't it easier to just use Charles Proxy (http://www.charlesproxy.com/) or mitmproxy (http://mitmproxy.org/) for those stunts? I can see the value for anyone not familiar with those tools, but for me as a developer, this is clearly something that can be solved without depending on a third party server.