Thanks for fixing.
BUTT is Boundless Universal Trade Tracker
It is also a web page and shows buy and sell prices of Boundless items. Data comes from a price gathering program which people can run to collect prize data.
As far as I know there is no API but you can directly go to pages. For example compact hard coal https://butt.boundless.mayumi.fi/#item=COAL_HARD_COMPACT
The page itself is just nested divs with speaking names. Should be quite easy if you want to parse it.