OneNote Diagnostics Tool is, as the name implies, a tool for helping gather data about OneNote issues enabling the Microsoft Support Team to address them in the most efficient manner.

All data relating to OneNote, which is obviously required on your machine for it to work, is collected into diagnostic and activity logs. This tool will help get the pertinent information needed to solve whatever issue you may be experiencing - you simply continue working as you normally would.

OneNote Diagnostics Tool silently stays in the background continually monitoring and storing activity as you progress through your day making all the collected details readily available to transfer upon encountering a problem that you may not be able to rectify.