Reusability asks whether an asset can be used in another product or context. A measure relates successful reuse to the assets offered for reuse. Reuse is an outcome, not a property of a library. The measure can count assets reused in another context, the effort saved, or the proportion of a new product built from existing assets. A catalogue of components with no consumers measures nothing. The context matters: an asset reused inside the same product is not the same as one reused by another team, and the draft's family is about the product quality property, so the measure should be specific about the boundary.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.