Within CTIOS, we have different set of event interfaces defined to process different types of requests. Here is list of few of those events:
1. Session Events Interface
2. Call Event Interface
3. Agent Event Interface
4. Skill Group event interface
5. Botton enablement Interface
Now for agent related events will be defined within the Agent event interface. There we have events methods named OnSetAgentStateConf. This confirmation message is triggered to the client to indicate that the SetAgentState request was received by the CTI Server.
You can get the complete details on the below link :
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cust_contact/contact_center/ctios/ctios9_0/developer/guide/UCCE_BK_C3995718_00_cti-os-developers-guide-ucce.pdf
Please review the above link once and see if this answers your query.
Let me know if you still need more information.
Regards
Hemant