Here is a Json example of the Communication object.
{
"Id": null,
"ContactId": 12345,
"TypeId": -1,
"CommunicationDate": "2026-06-11T13:45:00.9057393+00:00",
"Email": "",
"Subject": "",
"FilePath": "",
"AllocationTypeId": -1,
"AllocationId": -1,
"Notes": "",
"Completed": false,
"UserId": -1,
"SubTypeId": -1,
"DateAdded": "2026-06-11T13:45:00.9057393+00:00",
"PhoneNumber": "",
"Message": "",
"DiaryAppointmentDetails": {
"IncludeInDiary": true,
"ReminderEnabled": false,
"ReminderUnits": 0,
"ReminderTimeInterval": 15,
"UserId": -1
}
}