With the disclaimer that I haven't tried to set up any kind of agent-to-agent messaging so it may be obvious to those who have, what's the reason I would want something like this rather than just letting agents communicate over some existing messaging protocol that has a CLI (like, I don't know, GPG email)?
It is a fun problem to play with, but it turns out you can use anything. I use a directory per recipient and throw anything I want in there. Works fine, LLMs are 1000x more flexible than any human mind.