When getting a list response (whether optimized with listCache=true or not), it'd be nice to know which updaters were used:

• op, attr, class, desc, ctor (new one), notif are built-in updaters for MBeanInfo
• keys is optional built-in when listKeys=true is used (Additional JSON optimization mode #564)
• custom org.jolokia.service.jmx.handler.list.DataUpdater implementations may add more information. For example org.jolokia.integration.artemis.ArtemisDataUpdater adds RBAC information from AMQ.

I think it's worth to add some metadata to /version (and /config) responses.