Actually, in the 'vCloud Usage Meter API Guide' in the section 1.6 :
1.6 Operation Summary Syntax
Operations consist of an HTTP verb and a request URL. The reference documentation represents the verb and the URL using the following syntax:
HTTP_VERB /object_type/{id}[/action/action_name]
In this syntax, the initial / character is assumed to follow a site-specific API URL, such as https://vcaf.example.com/api. The following strings represent variables in the remainder of the URL:
the example url is confusing : https://vcaf.example.com/api
Better would be to state : https://vcaf.example.com:8443/um/api
Br,
Matthias