Interoperability asks whether the product can exchange information with other systems and use what it receives. A measure relates successful exchanges to the exchanges specified. The measure is tied to an interface and a message set, and both have versions. An exchange that succeeds against a mock and fails against the live system is not a successful exchange, so the test environment belongs in the definition. Interoperability covers sending, receiving and using the information, and a product can do the first two and fail the third. The measure should include the error handling for malformed or partial messages, because that is where interoperability usually breaks.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.