For FHIR REST and messaging endpoints, there's no appropriate code to identify the type(s) of content that can be posted to the endpoint. Furthermore, there's a standardized mechanism for determining what the endpoint is capable of that is dynamic and more accurate than anything that an endpoint registry could expose. Therefore, making the Endpoint.payloadType 1..* is inappropriate. It should be 0..*. Da Vinci CDEX expects to identify the endpoint to be a CommunicationRequest.recipient and there's no need for (nor appropriate value for) identifying the payloadType.