Minecraft wiki entry for till, associated text: Specifies the direction of Agent to till the block.
Must be one of:
forward to till the block on the front.
back to till the block on the back.
left to till the block on the left-hand side.
right to till the block on the right-hand side.
up to till the block on the top-hand side.
down to till the block on the bottom-hand side.