Plotly_hover questions (need to get exactly tooltip text)

Hi. We need to get exactly tooltip text that will be displayed by plotly.
As I understand we may to use plotly_hover for this. But plotly_hover gets points array as input. Questions:

  1. In what cases the length of points array will be more than 1?
  2. When length of points array more than 1, what point (what index of points) plotly will select to display tooltip?