What tool is recommended to smooth and add shine to the nails?

The recommended tool to smooth and add shine to the nails is the nail buffer. A nail buffer is specifically designed to create a smooth surface on the nails and enhance their natural shine. It typically has different grits or surfaces that can be used in a process that involves buffing the nail plate, thus improving its appearance.

Using a nail buffer helps in polishing the nails without damaging them, and it can help the nails look healthier, which is particularly important in nail care. The effectiveness of a nail buffer in achieving a shiny finish and a smooth surface is why it is a preferred tool in manicuring.

The other tools serve different purposes. A nail clipper is primarily used for cutting nails, which does not contribute to smoothing or shining. Nail scissors are used to trim nails with precision but also do not provide smoothing or a shiny finish. A nail file is intended for shaping the nails but does not have the same capacity to enhance shine and provide that polished look. Therefore, the nail buffer is the optimal choice for the task described in the question.