In the doc, in sections 8.9.5.2. http-listener Attributes, 8.9.5.3. https-listener Attributes and 8.9.5.4. ajp-listener Attributes, there are listed all available attributes for those listeners. There are also metric attributes listed in those sections:

request-count
processing-time
max-processing-time
error-count
bytes-sent
bytes-received

I think it would be more convenient to separate those metric attributes somehow from rest of the others (into separate table maybe?).

Why?

Those attributes are read-only and used for metrics (only when statistics for undertow is enabled). Moreover when user calls /subsystem=undertow/server=default-server/http-listener=default:read-resource he do not see them. To see them user has to call /subsystem=undertow/server=default-server/http-listener=default:read-resource(include-runtime=true)

How to distinguish whether attribute is a metric one? Execute /subsystem=undertow/server=default-server/http-listener=default:read-resource-description and search for "access-type" => "metric", e.g.:

"request-count" => {
    "type" => LONG,
    "description" => "The number of requests this listener has served",
    "expressions-allowed" => false,
    "nillable" => false,
    "access-type" => "metric",
    "storage" => "runtime"
},