The most frictionless tool I have ever seen is a piece of paper and pen.

It’s simple and easy enough to not think about anything else related to it. I don’t need to think about how I can use that, as my brain knows how to use it like I know how to eat. There are no disruptions like new interfaces where the button position has been changed, or performance glitches due to useless features. It’s just a tool that easily becomes part of your body, and you can start working immediately. Eventually it will disappear from your mind when you are using it. That’s how it becomes a perfect tool.