In some instances it can be useful to have a quick way of getting the list of all neighbours. Even if this is not available as a Cassandra metric, it is possible to get the information using Storage Service describeRingJMX (https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/service/StorageService.java#L1830), which is probably used only for nodetool describering

Also it can be useful as a way to determine ring information before scaling.