What does it mean when a game’s detail page says an amiibo figure is read-only or read/write compatible?
An amiibo-compatible game can have either read/write or read-only compatibility with an amiibo figure.
Read-only compatible means that you can tap the amiibo to the GamePad to get additional content. For example, the Mario amiibo will give you a special racing suit for your Mii™ character when used with the Mario Kart 8 game.
Read/write compatible, on the other hand, means that you can get additional content AND save certain game data to the amiibo figure. For example, you can customise your character and then save it to your Mario amiibo in Super Smash Bros. for Wii U. One amiibo can only hold save data for one game at a time.
You can still use an amiibo with save data on it in read-only compatible games. That means you'll still get the additional content without having to use a different amiibo!