For Mobile Agent or "Remote Agent", the support for it is in the SET_AGENT_STATE_REQ.

From the CTI Server Protocol Documentation:

For Remote Agent login, use ";" to separate the instrument and agent phone number in the
AgentInstrument field. Use RA_CALL_BY_CALL or RA_NAILED_CONNECTION in the
AgentWorkMode field for the Remote Agent login mode.

This should work for protocol version 13 or higher.