Cardiff's backer Vincent Tan is prepared to hand Mackay a £25million war chest for new recruits.
But the Scot will submit a dossier to the Malaysian billionaire owner before he hits the transfer market.
Mackay said: "It's not just about a gut feeling. I back my judgment - as we've done 20 times in the last 18 months. But there has to be a financial document which backs it up.
"Then there is the players' personal life, statistics and our thoughts. After that it's up to the owner whether to say 'yes' or 'no'."