It does not need a spec. It just needs to put a small print on "algorithm" and mention that it is using a cryptography library called libsodium. That's it.
As for the armchair field marshal cryptographers ranting around and nitpicking "useful projects", they are the same ones who praised Signal for their actual "state-of-the-art cryptography algorithm" for end-to-end encryption until they added a cryptocurrency coin in the messenger. Same with Keybase.
At least this project does not have such frivolous features and is only using libsodium like everyone else.
It is very easy to give "expert" criticism (constructive or not) on an open source project (since the project is transparent) but it is much harder for the critics to dive in and fix the aforementioned issues themselves. I would have much more respect for those who do both.