Ask HN: Top signs that a recruiter is wasting your time?

I am guessing a lot of people on here are currently looking for a job in software engineering, or are at least considering it. I've been looking to get back into it, so I've been chatting with maybe a dozen recruiters or more.

There isn't a better community than HackerNews when it comes to this stuff, so I'm curious what you all think and if you could share some of your experiences here.

What are some of the biggest signs that a recruiter is not a good recruiter? That they are wasting your time (i.e. that the lead is stale or too good to be true)? What are some ways to identify this immediately? Are there polite ways to be frank with recruiters? Please share your wisdom here!