1 of my runs has a piece of tarp over the wire on a small area for shade & feed protection, another has the coop up about 18-20 inches off the ground so the chickens can get underneath, & the duck pen has a piece of board across 1 end to shelter the food bucket.
However, that being said, all but my youngest birds tend to stand out in the rain like nothing is happening unless we get an absolute downpour. All 3 runs have coops/boxes with roofs. Mostly my extra cover is to protect food from rain. I even put my food under the coop on the one that is up off the ground. It's not really needed for shade as my coops are under several really nice shade trees.
I would say this: Make sure you have a sheltered area to place your feed & enuf shade to cover the majority of the birds if the sun gets too hot for them. Otherwise, as long as your coop is roofed & not too drafty, they will go in if they feel the need.