POST /api/v2/conversations/calls returning 400 Bad Request on agent proxy call

NICE CXone API & Integrations
1

Problem
We’re trying to trigger outbound dialing from a custom queue dashboard. The admin UI shows the agent’s outbound permissions are set correctly. The API keeps rejecting the payload though. We’ve been hitting the endpoint with a valid OAuth token, yet the response always comes back as a 400.

Code

POST /api/v2/conversations/calls
{
 "from": { "id": "0a1b2c3d-4e5f-6789-abcd-ef0123456789" },
 "to": { "phoneNumber": "+15551234567" },
 "wrapUpCode": { "id": "default" }
}

Error
Server responds immediately with a 400 Bad Request. Body just says “Invalid request format”. Doesn’t point to a specific field. We’ve validated the JSON structure against the docs multiple times. Honestly running out of ideas on this one. Headers look fine to me.

Environment & Steps

  • Pacific region org
  • OAuth token has conversations:write scope
  • Agent is currently in available state
  • Tested via Postman and Python requests library

Question
What’s causing the validation failure on the from object? The agent ID matches exactly what the UI returns. Still throwing the same error.