How to fetch the all user details of an Jabber user, such as firstname, lastname, phone numbers and other details:
We do not recommend using vCards. vCards are considered obsolete even by the XMPP standards.
UDS (User Data Services) might be a good alternative.
Request URL: 'https://<CUCM IP>:8443/cucm-uds/user/<user name>'
You can find it under 'Management' on Cisco Developer. 'https://developer.cisco.com/site/user-data-services/overview/'