Perhaps you need all this information from the agent. They need to give you clear detailed explanation of what they are doing for you. Are they providing the 800k? Are they opening bank account for you? Are you using own 800k money? What exactly is the agent doing for you?
If you're in home country, it's same thing you use there to show where you are living. Your rental, utility bill, drivers license, etc etc. If you're overseas already, hotel booking, entry stamp.