POST /api/v2/conversations/calls 400: Malformed participant address with SIP URI

NICE CXone API & Integrations
1

Hitting a wall with the POST /api/v2/conversations/calls endpoint. Trying to initiate an outbound call via the platform API using the TypeScript SDK. The request returns a 400 Bad Request with the error Malformed participant address.

I’ve verified the access token has conversation:call and conversation:call:write scopes. The payload looks standard, but the error persists. Here’s the JSON body I’m sending:

{
 "to": {
 "phoneNumber": "+15550199",
 "addressType": "phone"
 },
 "from": {
 "phoneNumber": "+15550100",
 "addressType": "phone"
 },
 "provider": {
 "id": "default"
 }
}

The from number is a valid outbound number in the org. The to number is just a test number. I’ve also tried using a SIP URI format for to (sip:+15550199@genesys.com) but that throws the same 400. The SDK method call is client.conversationsApi.postConversationsCalls(body).

Is there a specific format requirement for the phone numbers in the 2024.x API version? Or is this a known issue with the provider ID resolution?