Three of eighteen features could prove they were used, and none of them sold anything

A shopkeeper holding a hand tally counter turns to the bell over the door as a customer leaves, beside an open ledger headed tracking plan and an old cash register, under a blackboard that asks which event proves it is used and answers 3 of 18.

How a .NET and Angular shop got OpenTelemetry at both ends, a Grafana stack behind a switch, and a test that holds every feature to the event proving its use.