Remote (or CTI) answer functionality

The scenario is below:
1 Asterisk is used with SIP Server
2 Agent’s phone is behind Asterisk
3 Call is routed from the Asterisk and then to Agent’s phone
4 Call is ringing on Agent’s phone
5 How can I use AGI/AMI let the Agent’s phone answer?

Thanks!

The agent’s phone support Broadsoft SIP Access Side Extensions.
Can I use sip notify to Agent’s Phone Broadsoft extensions event talk?