Newb - I may be able to help you out depending on what you need. I'm very busy with school right now and have plenty of DGN things to work on (currently rewriting the donation bot from scratch and porting it to a new platform and framework), but provided what you want isn't incredibly elaborate I could maybe write one up for you or get you started in the right direction.
To
Cmp™,
HappySticks™,
Stan Radner, and everyone else saying bots are against the Steam EULA:
Officially, there's no ruling. Unofficially, it's not.
The quote that Cmp gave, "Subscription Marketplaces" is explicity defined as the Steam Community Market, with everything else being implied.
Steam may include one or more features or sites that allow Subscribers to trade, sell or purchase certain types of Subscriptions (for example, license rights to virtual items) with, to or from other Subscribers (“Subscription Marketplaces”). An example of a Subscription Marketplace is the Steam Community Market.
Certainly, Steam's trading function fits their definition of a Subscription Marketplace, but it's not specifically defined as such, and that's likely on purpose. Valve deliberately does not give explicit guidelines for questionable practices that they have a reason to allow, since it allows them to ban it (hopefully without as much backlash) at any time. A great example is the trading of items for cash; it's implied in the rules you shouldn't do it, but they've never said you specifically cannot because it stimulates the TF2 economy, it allows unusuals to be popular, and in turn makes Valve a bunch of money. Cmp's quote is specifically talking about scripts that automate Steam Community Market transactions, which Valve
very strictly enforces. Things like online backpack viewers fit into Cmp's quote, too.
Secondly, for those that don't know how trading bots work, they interact directly with Steam's API to to everything; put basically, they're sending bits of code to Steam and Steam is sending them bits of code back. It's not a simulated Steam client clicking on all the buttons. This API is publicly available. The trading API has very little reason to be public except for automation and/or interaction with autonomous programs, and yet Valve hasn't made it private (which they
easily could do). Historically, if Valve has provided an API for something, then you're allowed to use it. If they haven't provided an API for something (like for automating Steam Community Market transactions), then you shouldn't be doing it.
And for those
still skeptical, here's a screenshot of a support ticket I opened with Steam Support specifically asking about the legality of trading bots last July (and trading bots had already become popular by then) wherein, just like I explained above, they permit it while leaving it open ended:
TLDR: The quote from the Steam EULA is (deliberately) unspecific, Valve has publicly provided the tools that allow the automation of trading (that do basically nothing else) and they could have easily removed them (rendering most existing bots nonfunctional and not harming any of Valve's own stuff), and Steam Support has specifically said it's ok.
EDIT:
http://www.darklygaming.com/forum/threads/how-do-you-make-a-steam-trading-bot.11448/#post-172574
Rewards are coming in the next few days.
Rewards are coming in the next few days." and I started laughing so hard but then I realized what it actually said.
