CCS uses the vCenter APIs to make the connection. in CCS 11 you would add the credentials of a windows acocunt (Since vCenter is on a Windows machine). As far as I know, there is no Agent based solution to connect to ESXi. All of our access to ESXi is via credentials and vCenter APIs. Once you have successfully connected to a vCenter machine, then the ESXi servers that are being managed by that vCenter machine will be available to run ESXi standards against.