I think comments so far are too pessimistic. I design structures and believe this is essentially fine although much depends on the jointing. As it is open sided, wind resistance is not a major issue.
I’d agree with this. Much better to have joints on posts. You can do it your way but you will need a really well designed and constructed joint if you do.
True but I doubt there will be much sheer stress. The roof covering will act a bit like a sail so that is the biggest worry. If you glue and screw your slats, I think it would have enough sheer resistance. A bigger worry if the structure is not tied down is that it might blow over. Especially if you live near Chicago.
The “grooves” referred to are called birdsmouths where I come from. And yes, birdsmouthing over the supporting beam or plate is that standard method and much improves stability.
I think that is what you have indicated for the covering. No problem with weight unless you envisage really big snow loads.
Ideally, the posts would be mortice and tenoned into the beams and pegged. I think I might make the diagonal braces a bit longer, though they don’t need to be as thick as the posts. In the best work they too would be let into post and beam and pegged.
I presume this is to be freestanding. You show some kind of disc as feet. Not sure what that would be made of. If it’s bigger than the post base as shown, you need to be careful not to create a flat impervious surface that encourages water to be drawn up into the end grain of the post. There is some danger that each cross panel could move apart without any means of tying them together at the base.