Amiitool
In rust I have written an amiibo generator. It takes an NTAG id, an amiibo id, the keys (legally obtainable with homebrew), and outputs a signed amiibo. This was split into two libraries and 1 cli app. I didn’t like writing the core library - amiitool-rs - as it has a lot of cryptography. Cryptography is built such that 1 mistake means the whole output is wrong, making it very frustrating to debug. My code was broken because of a single byte not written. Amiigen outputs an unsigned amiibo given an amiibo id. Amiigen-CLI can do everything the original amiitool can do, but it can also generate a raw amiibo or a signed amiibo, given an amiibo id. I have used this to get all splatoon amiibo and legend of zelda amiibo, for the gear in those games.