For an after-hours service the phone is the front door. The service decides how calls are answered and triaged, how messages left for practitioners are recorded and passed on, how quickly electronic messages are acknowledged, and how urgent clinical content in any message reaches a clinician at once. Call handlers know the limits of what can be resolved by phone. Where the service offers electronic contact it tells patients the expected response time and that email is not secure for sensitive information.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.