Interesting, but at least the "top answerers" in given categories are just people who have answered a question in that category and have a lot of points regardless of whether or not those points were gained from questions with that tag.
Could you provide a direct example? I thought it was working in a different way.
The description is a bit opaque (https://api.stackexchange.com/docs/top-askers-on-tags), as it does not specifies what does "top" mean (but for sure they need to get some points in a given tag, within the last 30 days).
Thanks for sharing the source code as well:
https://github.com/stared/tagoverflow#tagoverflow