Injecting parameters in the DialogFlow CX conversation agent prior to start of dialog

[vertexaiExpert]

Hi, we are using DialogFlow CX and Conversational Agents/ Vertex AI to make outbound calls, but I need the agent to address the caller by name (ex. "Hi <name> this is ABC AI agent, we are calling to check on....") but we cannot find a way to give the default playbook the name parameter. It seems that the default book can pass parameters to other playbooks in the agent but it cannot take them from an API call or in any other way we've attempted. Can anyone please help? 

Thank you!