Installability asks how easily the product can be installed, uninstalled and reinstalled in a stated environment. A measure relates successful installations to the attempts, with time and steps. Installation is a countable event and a common source of support cost. The measure should include the clean environment, the time, the number of steps, the failures and the rollback. An installation guide is not evidence. A product that installs only after manual dependency work has a lower installability than one that installs from a package in one command, and the measure should reflect that difference. Uninstallation and reinstallation belong in the same family because a partial uninstall breaks the next install.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.