Fail safe asks whether the product moves to a defined safe state when it fails. A measure relates transitions to the safe state to the failures that should trigger them. The safe state has to be defined for the product and its context. It might be a stop, a hold, a fallback to manual control or a restricted mode. The measure is whether the product reached it, how long it took, and whether it stayed there. A product that fails safe but cannot be restarted has a different quality result from one that recovers. The evidence is an injected failure or an observed one, not a design description.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.