The MakeCallResponse includes UCID as globallyUniqueCallLinkageID. Alternatively, UCID is included in several Call Control events (e.g. Delivered, Established) if you have a Call Control monitor on the station. You may need to do some configuration on Communication Manager in order to have UCID sent to AE Services. There is some information on this in the following FAQ https://www.devconnectprogram.com/site/global/products_resources/avaya_aura_application_enablement_services/support/faq/tsapi/private_data.gsp#30
In order to know the current status of an Agent, you must perform GetAgentState.
I would suggest that you download the following from the Devconnect website:
1. "TSAPI for Avaya Communication Manager Programmer's Reference". DMCC Call Control features are provided by TSAPI and the TSAPI PG gives much more detail than the DMCC PG on these.
2. The DMCC .Net SDK. This includes the DMCC Dashboard which will allow you to test out the various DMCC features without having to write any code.