Some NFC figure collectors like to leave them in their protective packaging. This isn’t a problem for the Skylanders series, since they can be read through the boxes. However, Nintendo places a protective piece of material underneath every amiibo, which means someone must open or carefully tear through the box if they want to use it without opening it. That isn’t an issue with the Shovel Knight amiibo.
Yacht Club Games did not include the protective material. This means the amiibo can be held, in box, over the Nintendo Wii U Gamepad or Nintendo New 3DS touchscreen and read. A friend of mine told me he was able to do so with his, so I tried it for myself. While it is a bit cumbersome, especially on a New 3DS XL, it does work.
The Shovel Knight amiibo is immediately available for $12.99. It currently only works with both the Nintendo 3DS and Nintendo Wii U versions of Shovel Knight. As an availability advisory, the GameStop near my home only received three figures.