Section 3.1.2 of the MP Metrics spec states:
Tags can be supplied in two ways:
At the application server level by using MicroProfile Config and setting a configuration property of the name mp.metrics.tags.
This does not work in WildFly if the property is configured inline in the Microprofile Config subsystem like this:
Workaround: specify it under <system-properties> instead. This works as expected: