This ends up reading files into node.js and then running a command like grep but implemented in JS. I love the concept but isn’t this incredibly slow compared to native cli tools? Building everything in JS on top of just readFile and writeFile interfaces seems pretty limited in what you can do for performance.

In practice it is actually extremely fast because there is no process fork. You're talking nanoseconds for common commands

[Disclaimer: I made the thing]

Performance of the tools doesn't really matter when you have a full LLM inference loop in between each tool call.