You will need a one-direction opening gate. Installation should make certain that the door opens towards the landing, never the stairs. Most of the good baby gates for top of stairs do have some kind of mechanism that prevents the gate from opening over the stairs.
Evenflo Secure Step Top Of Stair Baby Gate.
Another great addition for this gate that comes as an extra is the hardware for attaching to round newel posts and banisters. You don’t even have to drill holes in your furnishing to mount it. In my mind this is without a doubt the best baby gate for top of stairs.
Pet & Baby Gates for Stairs | Evenflo
I have two of the Evenflo Top of the Stairs gates and I have been very happy with them. I installed them above two sets of stairs in my house. I thought the installation was pretty user friendly and easy. The key is that you need two flat services with studs or sturdy wood to install them on. You can't install them directly into the drywall. For me, I had to attach some 2x4's to the wall and then attach the gate components to that. The gates themselves are very sturdy and safe. I like that they are a neutral wood color because they don't clash with my decor. I even painted one of them to match the walls. Opening and shutting them is very easy once you get the hang of it but it's not so easy that the baby can figure it out or do it herself. I also like that when the gates are not in use, you can easily pop them out. For example, my mom has had this gate at her house for the past 8 years. Whenever the grandkids come, she pops the gate into place and then when we leave, she can take it out.
Top of Stairs Walk Thru Gate (Plus).