The data is served through a simple “api”, but there’s zero documentation and it’s designed for butt specifically, which means it can change as butt’s needs change. Angellus has “boundlexx” which is a more robust api with 800% more features, should come up a forum search.
The deal and courier modes were forbidden by the devs, anything that automates the process too much seems to be off limits 
It’s a muddy grey area since I’m positive someone has made a private tool that does the exact thing you’re asking for.
Quote from james
"If the tool started saying: “here is a list of items+location to buy from and another location to sell to” so that you can make loads of money <— then this is a clear unfair + automated advantage.
So the line is about the different between a fun tool vs an unfair money making scheme."