Hi !
As far as I know, evid and uuid are the same... Where you can find a difference, is in the MySQL database where the uuid is stored as a binary representation. Also, you can aknowledge an event using the zepfacade methods and an event's uuid. I never used the JSON API but using a dmd script, it can go this way:
zendmd
>>> from Products.Zuul import getFacade
>>> from zenoss.protocols.jsonformat import from_dict
>>> from zenoss.protocols.protobufs.zep_pb2 import EventSummary
>>> from Products.ZenEvents.events2.proxy import EventSummaryProxy
>>> zep = getFacade('zep')
>>> filter1 =zep.createEventFilter(uuid=u'43e33625-9dbb-42b1-a609-6750481b4c9b')
>>> eventDict = zep.getEventSummariesGenerator(filter=filter1).next()
>>> eventDict['uuid']
>>> evt = EventSummaryProxy(from_dict(EventSummary, eventDict))
>>> evt.evid
>>> zep.acknowledgeEventSummaries(eventFilter=filter1)
You should find out that eventDict['uuid'] == evt.evid and that your event has been aknowledged
Good luck,
--
Fayçal