alt Hacker NewsUNIX didn't really solve this scenario. Yes, you can limit what local files a user has access to. But with web applications and cloud services being so ubiquitous, the local boundaries are pretty much meaningless. Forcing an agent through an MCP is a way to grant access to remote services while still restricting how the network access can be used.
Network administrators also solved these things, e.g. you can limit what websites a virtual machine is allowed to access.
Now, if you’re letting your agents abuse network traffic there becomes a point where you’re criminally liable. Unfortunately the current US government has no interest in prosecuting such abuse.