anchorImageBase64s must be an array of 3 separate images, each cropped and ordered left-to-right as shown on the captcha. This order determines the order of points returned in solution.points.
Server returns errorId = 0 and status = ready. Read the answer in the solution field.
solution.points contains the coordinates (in imageBase64 pixels) of the 3 icons to click, ordered to match the anchorImageBase64s you sent. Click each point in array order.