That's FFI bindings. I need to provide the function signature of every API, because Erlang isn't statically typed. It's okay if some library provides it (like the linked , but I don't want to write this by hand if I can avoid it. And it's definitely not out of box, someone has to write the bindings for it to work

It would be different if I didn't have to write bindings and Gleam integrated automatically with foreign APIs. For Erlang that's probably not possible, but for the Javascript ecosystem it could make use of Typescript signatures maybe. (it would be very hard though)