If Auto-Tool is enabled, you can still click tools, scroll through the tools and then not be able to select anything. This seems counter intuitive and blocking things at the last step.

I propose one of two options:

1) When Auto-Tool is checked, do not permit Tools to be clicked, and show a tooltip that says you have to disable Auto-Tool

2) When Auto-Tool is checked, clicking "Tools" should automatically disable Auto-Tool and let you select a tool.

I like solution #2 personally.