A tour is a guided walk through a screen: a dimmed mask with a hole cut in it over one element at a time, and a card beside the hole saying what that element is. It is for the first visit to a screen that is already finished, not for a screen that needs explaining every time.
Reach for it when several controls only make sense together, when a redesign moved something readers already knew how to find, or when a feature ships into a surface people have been using for months.
- One control needs explaining? That is a Tooltip on the control, or help text beside it. It is there every time rather than once, and it is there at the moment the reader is actually looking at the control.
- The screen is empty on first use? An empty state with one sentence and one button beats a tour, because it sits in the space the reader is already reading.
- The thing is complicated? Documentation can be searched, linked and re-read. A tour is gone the moment it is dismissed, and nothing brings it back unless you build that.
- The interface explains itself? Then nothing at all. A tour over a clear screen is a modal the reader did not ask for, and it teaches them to dismiss the next one unread.
Keep it short either way. Four or five steps is a tour. Twelve is a manual with a mask over it.