Annotations: in need of more details especially about tags

1

I am currently quite interested in annotations.
Unfortunately most of the play examples (e.g. http://play.grafana.org/dashboard/db/annotations?orgId=1) produce an error:
Annotation Query Failed
HTTP Error (502) Bad Gateway

Are there other working examples preferably with tags?

I understood so far that there are
title (heading for the event),
text (for a more detailed description of the event),
and tag(s).
What are tags for in this context?
For us it would be very handy to filter the annotations of graphs within the same dashboard, so some would not have all the annotations (at the moment it is only possible to turn annotations on or off for all graphs within the same dashboard it I am not mistaken).

2

Tags are just another info field shown has a tags in the annotation tooltip, you can filter on them as any properties (depending on your datasource), but they still show on all graphs