In the API reference, what should I be entering for "server_url"?

What is the proper data for "server_url"?

NPM

I suspect you're looking at the Response XML, not the Request XML.  There is a problem with the Javascript in the PAWS API reference.  It's supposed to show you only the Request when you click on the Request link, and the Response when you click on the Response link.  Right now, both the Request and Response appear simultaneously.

The Javascript should be fixed soon.

I use the xml namespace value returned in the request to GetApiVersion to set the namespace in my requests. In the version of CUCM I'm currently using, it is https://developer.cisco.com/docs/webex-xml-api-reference-guide/#!getapiversion