Add note about metrics not being sent from a send only endpoint (#7213)

Author: soujay

monitoring/metrics/index.md

@@ -44,7 +44,7 @@ To enable collecting metrics in an environment:
 4. [View the performance data collected for endpoints in ServicePulse](in-servicepulse.md)
 
 > [!NOTE]
-> [NServiceBus monitoring setup tutorial](/tutorials/monitoring-setup/) is an in-depth, step-by-step tutorial about installing and configuring everything to get the most out of performance monitoring.
+> [NServiceBus monitoring setup tutorial](/tutorials/monitoring-setup/) is an in-depth, step-by-step tutorial about installing and configuring everything to get the most out of performance monitoring. The metrics feature can't be used on send-only endpoints.
 
 
 ## Performance impact on system resources

monitoring/metrics/install-plugin.md

@@ -11,6 +11,9 @@ redirects:
 
 The `NServiceBus.Metrics.ServiceControl` component enables sending monitoring data gathered with `NServiceBus.Metrics` to a `ServiceControl.Monitoring` service.
 
+> [!NOTE]
+> The metrics feature can't be used on send-only endpoints
+
 ## Configuration
 
 The package allows collection and propagation of metrics to ServiceControl.
@@ -19,9 +22,6 @@ It can be enabled via:
 
 snippet: SendMetricDataToServiceControl
 
-> [!NOTE]
-> The metrics feature can't be used on send-only endpoints
-
 ### Service Control Metrics Address
 
 The default instance name is `particular.monitoring` which is also used as the input queue for ServiceControl monitoring.

tutorials/monitoring-setup/index.md

@@ -59,7 +59,7 @@ scinstance --> pulse
 
 A running NServiceBus system can be configured to send data about its operations to three main queues:
 
-- `Monitoring`: Each endpoint will gather and send metric data to this queue. This data holds information about the health and performance of an endpoint.
+- `Monitoring`: Each endpoint will gather and send metric data to this queue. This data holds information about the health and performance of an endpoint. Metrics are collected only when an endpoint receives and processes messages and hence send-only endpoints will not emit processing-related metrics.
 - `Audit`: When an endpoint successfully processes a message, a copy of the message will be forwarded to this queue. The audited message will have additional headers which contain data about the processing of the message.
 - `Error`: When an endpoint fails to process a message (after exhausting automated retry attempts), a copy of the message is forwarded to this queue. The failed message will have additional headers which contain data about the failed attempt to process the message.