In some cases, you would like to know when one of your tags disappears from some of your systems. It is possible to set up a monitor for such an alert scheme within Datadog:

1. Set up a classic metric monitor, and specify the metric and tag that you want to be alerted on when it is missing.
2. Select an alert condition that could never be triggered. For example, a < -1 for a positive metric such as system.cpu.user.
3. Activate the Notify if data is missing option, as you can see on this example:

Your alert triggers if the tag stops reporting.

Additional helpful documentation, links, and articles:

Learn how to create a monitorDOCUMENTATION Configure your monitor notificationsDOCUMENTATION