You know what's not a good idea? Telling the person screening my calls that I'll "know what the call is about" and refusing to elaborate further, when in fact I have no idea who you are and we've never spoken before.
You know who does this, aside from overly aggressive salespeople? Job candidates who think that this brilliant trick to get them past the gatekeeper will help them get hired.
You know what happens when they get put through to my phone line? I let the call go to voicemail, listen to their message, discover they're calling about a job, and immediately forward their message back to the original person they spoke with, with instructions to call them back and tell them we don't take unsolicited calls about jobs.
You know who immediately ruins any chance of me considering their application? People who do this, demonstrating total disregard for honesty or our clearly stated policies that we don't take unsolicited calls about jobs. I put that policy in place for a reason. I'm sorry that you don't like it -- but it's not there for you; it's there to help me. But at least now I know that I don't want to work with you.
I know there must be job search "tips" out there that encourage this ridiculous practice. I want to hunt down whoever is encouraging it and slap them.