Setting a value higher than 0 makes the corners of toolTip rounded. Higher the value, more rounded the corners are.
var chart = new CanvasJS.Chart("container",
How to make rectangle tooltip to circile, then is there is any posibility adjust tooltiop position
Since Tooltip is a DOM Element, you can set its style via css as shown here in order to make it circular. But, there is no API to control its position yet.