Get all labels for a board using REST API

Hi,

I have defined some labels for a board and want to get them all using the REST API. For this I thought it would be good to use the following call: http://community.lithium.com/t5/Community-API/bd-p/developers-rest-api?leaf-id=Board.labels#Board.labels.labels

But instead of getting all the labels I only get the label which are currently used in a message. What call should I use to get all. The goal is to show something similar to this: "no messages for this label. write the first one."

Any hint would be great!

Thanks,

Michael