When looking at the this question, I wanted to see what topics had recently been decided were on or off topic. I noticed that there were two tags off-topic and on-topic and they were used rather inconsistently.
For example a question would be "Is this on topic" and be tagged with off-topic or vice versa. There were even questions with both tags used.
Questions about whether particular topics are off or on topic.
However there is also the scope
Use this tag when examining what is on-topic or off-topic, and why.
and there is the topics which has no usage guidance but is used in much the same way.