Backend service is definitely way to go if you want to serve models for the user.

So Bash and Edit tools are a bit weird, Bash tool is essentially JS execution, and Edit tool automatically generates a script that performs the edits on the page. These tools are needed for the model to explore the page, whatever it does at the end it creates a separate script that will be applied on the page load.

Oh neat. So the edit tool is like a convenient API/wrapper for it to eg add HTML to some element? I guess theoretically that can also be achieved through Bash as well, but the tool fits closer to an interface we know exiting agents are good at.