service/prometheus.md

-[Prometheus][] is a monitoring system that is designed to process a
-large number of metrics, centralize them on one (or multiple) servers
-and serve them with a well-defined API. That API is queried through a
-domain-specific language (DSL) called "PromQL" or "Prometheus Query
-Language". Prometheus also supports basic graphing capabilities
-although those are limited enough that we use a separate graphing
-layer on top (see [Grafana][]).
+[Prometheus][] is our monitoring and trending system. It collects
+metrics from all TPA-managed hosts and external services, and sends
+alerts when out-of-bound conditions occur.
+
+Prometheus also supports basic graphing capabilities although those
+are limited enough that we use a separate graphing layer on top (see
+[Grafana][]).
+
+This page also documents auxiliary services connected to Prometheus
+like the Karma alerting dashboard and IRC bots.
 
 [Prometheus]: https://prometheus.io/
 [Grafana]: howto/grafana
@@ -13,6 +16,9 @@ layer on top (see [Grafana][]).
 
 # Tutorial
 
+If you're just getting started with Prometheus, you might want to
+follow the [training course](#training-course-plan) or see the [web dashboards section][].
+
 ## Training course plan
 
 - Where can I find documentation? In the wiki, in [Prometheus service