Unity is integrating a similar but more production-ready tool, Muse Animate, with their Muse platform. It does text-to-animation, and can fill in motion if you just provide keyframes. See usage here: https://youtu.be/tMCPz_yI7pY?si=OXAyxgGxHbCDywHm

I would love to use this in addition to Mixamo, which is where I get 99% of my animations from; the other 1% is badly-animated keyframes.