Open the tutor.
Click "Tutor settings" in the lower left.
Click "Grading" on the left-hand side.
Adjust the rubric in the textbox as you see fit.
Be specific.
Mention specific learning targets (e.g. mastery of content, ability to reflect, ability to argue points) you would like tutees to show
Use the revise feature to talk to the AI and have it revise the rubric for you.
This helps prevent rules that might contradict each other. You can view the changes and make further changes, as needed.