The squared notebook gives a nice line to follow for the cuts. Any tool should aim to exactly fit these lines, just to enhance the feel of the finished tab.
The very square edge is a little open to becoming frayed and bashed, so the tool should be a curved die giving a nicely rounded corner to the tabs. Either the square shallow tab as shown here, or a deeper semi circular version would be nice. I clipped only 5 pages at the start of a section.