Read+Write feature:

Call in backup Pikmin

More can be called in as the amiibo levels up.

Read-only feature:

Call in four backup Pikmin

Read-only feature:

Figure appears in-game and can be collected to gain energy points

Unlike with most games' amiibo features, only these exact figures are compatible (not other figures or cards of the same characters). For example, Luigi from the Super Smash Bros. series doesn't work; only Luigi from the Super Mario series does.

Source: Mon Amiibo / Thanks: memoryman3

Read-only feature:

Make a random other figure appear in-game to be collected

After the Pikmin figure has been scanned and collected, scan it again to make other amiibo figures appear without needing to scan them.

Thanks: Alex Oatley

Read-only feature:

Receive some energy points, once per day

This feature works with any amiibo (with the possible exception of those that work with its other features).