I've been quite keen on the new FFI too - apologies if this is old news, but have you tried the [0] jextract stuff for some of the boilerplate gubbins?
No! Thanks for the callout! That would certainly help on my path. My main goal was to insulate calls to avoid overly complicated reference counting when integrating large native surfaces into as Java program, but certainly an important aspect is getting the function signatures to target in the first place. I threw something bad together to work sort of like this (testing using proton), but I'm more than happy to bin it for something that just-works.
Intellij (and all the other variations) has something very similar to this called [0]HttpClient. Being able to commit and basically just read the file is very useful. You can also do validation and scripting with it too.
I've been a happy Kagi user for a few months now. As someone else has already mentioned, shopping etc is often better elsewhere, but for 95% of my search I use Kagi exclusively.
https://api.enterprise.wikimedia.com/spec/spec.yaml