I found some documentation on profile tags at Add Player Tag which says the following:
This API will trigger a player_tag_added event and add a tag with the given TagName and PlayFabID to the corresponding player profile. TagName can be used for segmentation and it is limited to 256 characters. Also there is a limit on the number of tags a title can have.
How do we find the limit for a title? What is the limit on the string attached to the tag, not the tag itself?