Replaceability asks whether the product can replace another product in a stated context, and be replaced by it. A measure relates successful replacements to the replacements attempted. Replacement is a migration, and its evidence is a completed scenario, not an interface similarity. The measure should name the product being replaced, the data and integrations involved, and the criteria for a successful replacement. It often matters more to an acquirer than to a developer, which makes it a good family for a tender response. The reverse direction, being replaced, is part of the definition and is often forgotten.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.