I agree with Belinda and Dom.
"Just to be clear" is usually used when you are ensuring someone else understands what YOU want. (It can come off as demanding/commanding if you use the wrong tone.)
I usually use "to clarify" instead. It doesn't always focus on what I want, but rather to make sure we are both understanding the same thing.
1. Just to be clear, I don't want to you to include any potatoes in my meals this week.
2. To clarify, I don't want to eat any potatoes this week.
3. To clarify, we agreed that no potatoes would be served with any meals this week, right?