Are the VK API responses documented somewhere?

Question

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Actually, subject. I am writing an application for Vkontakte, IFrame.
I see the request parameters in the documentation, but I can't find a description of the response format. It is clear that there is JSON in which error or response , but what exactly will be inside this response ?!
It's just that methods like apps.getLeaderboard give nothing but an error until the app is in the . And it cannot get into the catalog until social functions are implemented in it.
I feel like an idiot who missed the “heavenly briefing”: I understand that this should not be so, and I don’t see the cries of other beginners on the Internet with the same question. But I don't see a way out of this vicious circle either. Poke your nose, please.