Set call-inactivity alert thresholds from healthy periods only

When choosing a "no calls for N minutes" alert, do not size N from all historical gaps between calls. The longest gaps are usually outages, the very thing the alert should catch, so they push the threshold too high. Calibrate on known-healthy business hours, scope the alert to every live number rather than one environment label, and use two simple signals: no received calls and no completed human handoffs. Base the handoff signal on a durable handoff-complete event, not a transport-level "transfer completed" field. Alert rules must treat missing data as unhealthy, and a separate watchdog should report "monitoring unavailable" when telemetry itself stops. Treat historical gaps above the threshold as periods to investigate, not as proof the alert would be noisy.

Applies when: setting call-volume or inactivity alerts for a phone or voice-agent service. Keywords: call inactivity alert threshold no calls monitoring Grafana missing data voice outage alerting handoff business hours