Last week, Zrakor posted to the forums stating that there are some mission tags that are not available to players through normal game mechanics and that these tags would be added to the game with the next patch. The patch will be Tuesday, 25 January.
Until the patch, if you have one of these agent offers, you may petition and a friendly GM will give you the tag. Please petition only if you have one of these mission offers. After the patch, it will be neccessary to get the tags through normal means in the game.
More information, including the list of tags, can be found in Zrakor's forum post.