You need to closely screen and supervise your recruiters. Start with an open-ended question: "how would you go about sourcing candidates for XXX position", "how would you screen them", "how would you entice them"? Listen closely to what they say and if you do not feel comfortable this would yield you the candidates you are looking for, fire the recruiter and look for one that would understand your needs.

Recruiters, like any other service professionals, are always trying to sell you on their experience, but you owe it to yourself to closely inspect their claims and methods. If recruiter is any good they won't be offended and would cooperate.

Contingency fee recruiters are especially renowned for sloppy work. If they only get paid when they place a candidate their only incentive is to sell you the first warm body they find. This type of attitude you have to nip in the bud.