A blurb is that little bit on the back of a papaerback book that gives you an idea of what the book’s about and entices you to read it.
On Wattpad, it’s that little bit next to the cover. The first sentence or so is what shows without clicking on it, so you want that first sentence describing your book to be something that at the least, won’t make someone skip it all together.
The best way to see is to look up your book, see what users see.
For myself, “John was the bad boy,” turns me off. For others who like bad boy stories, it would draw them in. You have to know your audience. It’s kinda hard sometimes making it hook a reader without giving away the plot.