So many things to address, so little time...
I mean, it's only a tractor cover, so no need to build the Hoover Dam, but on the ground (vertical force) you could have simply dug in 6" and put a couple of concrete pier bases on some gravel and you'd have prevented horizontal movement. Also, the piers spread the load and would avoid your posts sinking, but the splayed pins should also resist this force. Same thing at the top: were the "beams" bearing on the posts, or were they ledgered? Bearing is proper, but here, ledgered is likely enough. Also, the rule for cantilever is the overhang only 50% or less of the supported beam, which I see you are in violation of here.
At the hill-top, the danger is a water-logged softening of the ground and the entire array of pins pulling away, particularly if water can build up at the slope/roof junction, which it can't. Here though, the large opening b/w the slope and the roof will allow rain and snow to enter the rear of the structure and saturate more of the slope. This could be the structure's achilles heel. Again, with few opposing forces (structure weight, snow load..), this should last. And even if it doesn't, the structure would want to pivot on the posts and still miss the tractor! Only the pins will keep it standing. Not sure if that makes them a good thing even so...
As someone else pointed out, the welds do not look like they penetrate, particularly on the channel/angle. Again, this is a tractor awning and even a weak weld should hold this up. Here, strength in numbers is really a thing.
I build a lot of things: some require inspection, some don't. Thankfully this cover falls in the "don't" category. I'm all for squeezing use out of little bits of flat land - I live in the mountains too - so I'm confused: somewhere between "good for you" and "too hillbilly for me."
As long as the tractor comes to no harm, I think we're good.