How to Trigger a Master Agent based on Transaction Received on Another Agent

In TB there are two agents. One of the Agents is a reactive Slave for a Serial Bus protocol. It receives commands on the Slave serial port and then needs to generate APB transactions on another agent to execute Read/Write Commands received from Master. Based on APB transaction Status a response needs to be sent to the Master on the Serial interface. Please suggest
What is the best way to communicate between two agents to Pass Command from Slave Agent to APB master agent ?
Get Response from APB master Agent and send it back over Serial Interface ?