It seems that all tags have an internal ID, for instance here on stackapps, the api-v2 tag has ID 2442 which you can only see if you edit the api-v2 tag.

As far as I can see none of the APIs expose the ID, not 1.1 and not 2.0.

But this makes it very hard to implement some useful things, like detecting tag renames since the only ways to get at tags is to look at all of them or refer to them by name.

It seems a tool that watched your favourite tags and let you know when any renamed would be fun/interesting/useful. Is there any reason why the tag ID numbers are not exposed?