I have used janet for embedding into another program as an alternative to lua and it was great for that case. Lua doesn't have good tooling either, and I didn't have anything to gain from a tiny runtime and I wanted more powerful tools for making a DSL in there. It worked out perfectly, I'd do it again.

I personally like Fennel a lot, but it’s not at the point where I would build something large on top of it. The language itself is solid, but like you said, there’s not a lot of tooling.

It's complicated; Calvin Rose was the original creator of Fennel ("fnl"), but I understand it was just a little side project that he made over the course of a week or so in college. Phil Hagelberg found the project years later and thought it was cool, took over as its maintainer, and basically turned it into the Fennel you know today. So it's like, kind of, I dunno, both things are kinda true.