POST /api/v2/conversations/calls 400 on participant address

Trying to spin up a simple outbound call via the API and it keeps dying with a 400. The docs say the address format is straightforward but I’m clearly missing something on the structure. Here’s the payload I’m sending:

{
 "to": [
 {
 "phoneNumber": "+15551234567"
 }
 ],
 "from": {
 "phoneNumber": "+15559876543"
 },
 "wrapUpCode": "none"
}

The error response just points to to[0].address being invalid. I’ve tried adding type: "phone" but that didn’t change anything. Am I supposed to wrap the phone number in an object differently or is there a specific format Genesys expects for the phoneNumber field inside the address block?