Outbound contact list POST returning 403 INVALID_VALUE

Trying to push a new contact list via the Outbound API but hitting a wall with 403 INVALID_VALUE. The payload looks valid against the schema, yet the server rejects it immediately.

  • Endpoint: POST /api/v2/outbound/contactlists
  • Content-Type: application/json
  • Auth: OAuth2 bearer token with outbound:contactlist:write
  • Payload: {"name": "Test List", "type": "SFTP", "contactListItems": []}

Here is the exact error response:

{"code": "INVALID_VALUE", "message": "Invalid value for contactListItems", "errors": []}

The contactListItems array is empty, which should be fine for creation. Is there a hidden validation rule in Kotlin’s Jackson serialization or a required field I’m missing?