Telemetry

The numbers a running system reports about itself, continuously and without being asked: how many requests came in, how long they took, how many failed, what it cost, how many tokens (the word-pieces you're billed by) it got through.

The readouts on the van dashboard. Fuel, temperature, miles done.

Which is precisely how it differs from observability, the term sitting next to it: telemetry is the readouts. Observability is whether those readouts are good enough to work out why it broke down. Numbers, versus being able to explain them.

Why it matters: telemetry answers the management questions rather than the technical ones — what is this costing us a week, is it getting worse, is anyone actually using it. One caution worth carrying: measurements can quietly capture private information, so what gets recorded is a privacy decision as much as a technical one, and it's fair to ask what's in it.

Related: Observability · Logging · Token cost / cost discipline