Whilst most recruiters will prepare their candidates to some extent, they are often reluctant to prepare clients as they feel it would be too patronising.  Of course, the last thing we want to do is patronise but there is often a value in ensuring that they sell the role to your candidate.  If you can let the client know what it is about the opportunity that will appeal to the candidate’s motivations, then they are more likely to gain the candidate’s interest in the role when they interview them.