Some things that I take to be a good sign that I should work with a recruiter: they want to discuss what you want AND then actually use those notes. One of my first jobs came about because a recruiter called me, talked about what I wanted and then called me back 3 months later when he had an open req that fit my profile. Those I value.
what is the name and location of the company? is the position permanent, contract or remote? what is the salary / hourly rate? what are the benefits (if any)?
if they are not willing to answer those simple questions, then they aren't worth your time.
these companies are a dime a dozen. you can also find the same opportunity advertised by 10 different companies so don't think that by not entertaining one of these companies you will be missing out on the opportunity. I think that is why candidates waste their time with the scrupulous ones... they fear that if they don't bow to these companies, they won't get the job... not true at all.
Honestly, they're also as useful as used car salesmen as well. It's a dirty job. I seriously considered doing it before, but couldn't really cope with the environment.