User assistance asks how well the product helps a user who is stuck. A measure relates successful help to the help offered, or support demand to the tasks performed. Help takes many forms: inline hints, a help centre, a chatbot, a person. The family is about the product's assistance, so the measure should start with the point where a user needs it. Two useful shapes are the proportion of help interactions that resolved the problem, and the support contacts per unit of use. A help centre with excellent articles that nobody finds is not good assistance. The measure should record how the user reached the help and whether they returned to the task.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.