The question that separates them.
Ask who pays the person you are dealing with. A trading company is paid by you through a margin you cannot see, which is legitimate and worth understanding. An agent should be paid by you and by nobody else, and an agent taking a commission from the factory has an interest in the factory you were not told about.
We charge 5 per cent of the order value, paid by you, and we show you every supplier invoice. That is the model, and it is the reason the number is on the homepage instead of behind an enquiry form.