Hi Dinh.  Thank you for your question.  A professional headhunter (HH) will tell you as much as they know and can share with you, meaning there will be confidential information entrusted to HHs that they cannot disclose.  If your HH cannot give you adequate information on the opportunity, maybe that HH is not a professional one!  A professional HH will tell you all you need to know about a client and a role, and a good candidate will also carry out their own due diligence on the client and the role - it's a two way street.  If you find at any point that your HH has withheld important information you deem necessary for you to make a decision, you should "fire" your HH and seek out a better career partner.  What are the signs?  Inconsistent inormation you receive from your HH and the info you get from the client interview or from other valid sources..info such as salary details, career progression, job title, report lines, why the roles is open, etc.