This is a really tough question. Basically what Ancient Lady says is true. Pretty much anything running Android 3.2+ will run AGK. However, many device manufacturers decide to not support OpenGL or strip some OpenGL functionality out for hardware compatibility reasons. How do you know this? You don't. You also cannot specify what OpenGL compatibility you need. For example, I have found a small number of devices that have stripped out OpenGL's mipmapping support. Why? Who knows! Probably because they put in cheap GPU that overheats when using this feature.
Unfortunately there is no way to tell this.
It would be nice if things like OpenGL mipmapping support was checked by the AppGameKit implementation of OpenGL and just didn't use it when it isn't supported. What would be better is if Google allowed developers to explicitly specify those options.
I'm not sure why anything on the Google Play store would say "Requires Android". That's a given... That's like the App Store saying "Requires iOS"...