In this long post, I will describe a few issues associated with tags that I believe should be solved. Feel free to add your opinions regarding the issues or specific tags (or feel free to edit this question to add more issues or tags)
Tags that should NOT exist
I've observed that, on this website, there are a lot of tags whose meaning is not widely accepted yet or it is not understandable.
For example, unassisted-learning. I've never heard of this expression before (and I am involved in the field of AI). Even though an expression occurs in a web article, it doesn't mean that it deserves a tag on this website.
I believe that only topics that have a "considerable amount" of associated research literature should have an associated tag, for example, questions related to ant colony optimisation (ant-colony) or related to on-policy or off-policy RL algorithms.
There are other tags that I believe should not exist on this website:
bayes should not exist because there are more meaningful tags (with respect to AI), such as bayes-theorem (which already exists); maybe we could also have the tag probabilistic-graphical-model (which includes e.g. Bayesian networks, whose tag bayesian-network already exists) for some questions that are currently a little bit ambiguously tagged with bayes); some of the questions that are currently tagged with bayes can instead be tagged with naive-bayes (which already exists).
learning-algorithms (there is already the tag machine-learning, which includes all machine learning algorithms; futhermore, AFAIK, learning algorithms is not a standard expression, whereas machine learning is.).(it makes sense to have a tag "learning algorithms" because machine learning is not just about learning algorithms, but also about models)
software-evaluation (this has nothing to do directly with AI; this tag should really not exist on this website, IMHO)
structured-data (I have no idea why this tag should exist)
challenges (there are challenges everywhere; this tag is very vague)
embedded-design (maybe this tag should not exist)
imperfect-information (I know that there are games with imperfect information, but maybe this tag should not exist)
gaming and game-ai (I would delete both of them and just have a new tag games, which will include everything that is related to games in the context of AI; also, do we really need these tags, if we already have game-theory (which, IMHO, should exist on this website)? anyway, the description of the gaming should be updated, given that now we have a tag called combinatorial-games)
probabilistic should not exist because it an adjective and it not widely used; the non-existing tags probabilistic-model or statistical-model would have been better; anyway, the tags math or statistical-ai should somehow already cover associated questions, so I suggest to delete probabilistic(temporarily solved by renaming it to probability).
brain maybe should not exist because there is already biology, which should include all questions related to biological inspired AI, but maybe we can also keep it (given that the brain is an important inspiration)
ultraintelligent-machine (there is already superintelligence, and ultraintelligent-machine is, AFAIK, not very common; a more common expression would be universal-intelligence, but I would just have superintelligence)
In general, as a rule of thumb, if a topic or expression does not have an associated Wikipedia article, it likely means that a corresponding tag should not exist on this website. I have not given a motivation for each of the tags, because otherwise I would not do anything more today. It is possible that in some cases I am not seeing the reason of the existence of the corresponding tags. However, I believe that most of them should not exist.
There are tags that are duplicates
It is possible there are a lot more duplicate tags.
Tags that need improvement
There are tags whose definition is not clear or inconsistent with the existing posts on this website. For example, the tag chat-bots, whose current definition states
For questions about chat-bots. NOT for questions about how to program a chat-bot, as those kinds of questions are off-topic.
However, one of the highest upvoted question on this website with this tag is What are the latest methods to train a chat bot?.
Other tags that possibly needs improvement are biology and brain. In their current description, they have no relation to AI (so they should not even exist). These tags could be used for questions that are both related to biology (and the brain) and AI at the same time (e.g. human-inspired AI, whose tag, btw, already exists on this website).
I suspect that there are a lot more tags that need an improvement, in terms of description and scope.