Wait, I thought more people knew about generating Candid from Rust code. You can see it in this thread: Automatically generate candid from rust sources - #3 by senior.joinu
and I set up auto-generation on my IC Canvas project because I cannot be bothered to hand-code a candid declaration. If you tag your methods, you can use the export_service() pattern to auto-generate: canvas/api.rs at main · krpeacock/canvas · GitHub
We definitely need to document this flow and add it to our Rust examples