Miller is a great cli tool to work with structured text data file.
The tag description could be:
Miller is an open source command line utility: it is like awk, sed, cut, join, and sort for name-indexed data such as CSV, TSV, and tabular JSON.
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Unless the tool gains a large amount of popularity and becomes as common as awk or sed I'm going to say that for now we don't need the tag.
We shouldn't create a tag just because a named tool exists, especially when there are better and more relevant tags, as suggested by Ramhound in a comment, of json and csv.
Unless it gets to a point where someone has to use Miller to achieve something, and we have a lot of questions where only Miller is the answer, or we are getting a lot of questions about it then the specific tag serves no real purpose except separating questions from their more general audience who could suggest different ways with other tools.
From a quick search I can see perhaps two questions that might be worth tagging. That's not really enough for me to consider it worthwhile.
At an absolute minimum we want the excerpt to be more than just copy-pasted information from the tool website. From our review queue rejection reason:
Simply defining what a [tag] is rarely helps those using it unless the tag's name itself is ambiguous. Excerpts should describe why and when a tag should be used. See the help center for more guidance.
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