How to show the restrictions for the file upload?

This is used for the b2b web tool. The user can upload an image file by clicking the "upload" button. There're 2 restrictions: max size and file formats.

What is the best way of showing that?

1. Put a short general description under the upload button and open a tooltip on click or hover
2. Same, but add the max file size to the button
3. Place the list of all restrictions under the button (I would choose this option if there's not so many file formats)