POST /api/v2/conversations/calls returns 400 when passing agentId in payload

Trying to kick off an outbound call via the API so the agent doesn’t have to click the button. The goal is to have a backend service trigger the dial when a specific flag is set in our CRM.

Using the POST /api/v2/conversations/calls endpoint. The docs say I need to provide an initiator and a participants array. I’m trying to set the agentId in the participant object so the call routes correctly to their queue.

Here is the JSON payload I’m sending:

{
 "initiator": {
 "id": "my-oauth-client-id",
 "type": "application"
 },
 "participants": [
 {
 "id": "agent-uuid-from-token",
 "type": "agent",
 "callType": "outbound",
 "targetAddress": "tel:+15551234567"
 }
 ]
}

Getting a 400 Bad Request with this error:

{
 "message": "Invalid participant configuration",
 "errors": [
 "Participant type 'agent' requires a valid queueId or skillGroup"
 ]
}

I’ve verified the agent UUID is correct. I’ve also tried adding a queueId to the participant object, but then it complains that the agent isn’t eligible for that queue.

Is there a specific header I’m missing? Or is the targetAddress format wrong? I’m using Postman to test this before moving it to our Node.js service.