I'm holding a number of offers (as a candidate) at the moment, and here's my experience.

- The good recruiters have a high hit rate and are quick. One of these guys called me about 4 weeks ago. We did a chat about my history, and what I wanted. The next day, he suggested 4 firms. The day after, I had 3 interviews booked. This bit is the real value: if they are good they will suggest people who have a chance of wanting you. The last firm never responded, which I'll chalk down to the hiring firm being disorganized. I've been there myself, so I don't mind. But 3/4 is pretty decent for an interview rate. Got an offer from one of them, and another one wanted to talk about stuff to explore, but were more wanting to explore with me than having a specific thing to do.

- High hit rate comes from good relationships. There's a group of firms that are very picky with their hires (FAANG, HFT) that every recruiter in London will mention to you if you are a dev. Knowing which ones actually know these hiring managers is hard. They all claim to have gone to school with them. But also, the filter is pretty generic. If you look like a good coder, you will get an interview if the firm is hiring, regardless of whether the rec knows the guy. And past that there's nothing the rec can really do for you. So what are good relationships really? They're when there's an exclusive relationship. "I have this role at this salary for this profile, go and find me 4 CVs". A good rec will return with 4 CVs, one of which is wrong, and 3 candidates. The firm can now interview two of them and get the first one that works (and wants the job), knowing that probably the backups are just as good and one of them will want it.

- The less good recruiters have the goods but can't move the conversation forward. A couple of firms were in the same position as the offer above, same kind of role, weeks before. If you just take it easy, candidates will pass by. "Hiring manager is really busy, they're expanding, but they want to talk to you" just sounds a bit silly after a few weeks, and as a rec you need to move the hiring manager. What is fast? A guy is calling me today, on the weekend, knowing that I have offers (yes with details), having phoned me on Friday. That's giving yourself a chance.

- The really bad recruiters don't know how the business works. As a CTO I get this from the other side. I have a load of emails from various randoms along the lines of "Angular engineer, £60K, available immediately". There's no reason to think I'd want one of those, it's just a spray and pray. The whole point of the recruitment industry is to be a broker. You wouldn't run a dating agency where you just randomly tried pairing people either. Or a real estate agency where you randomly match people with houses in random places. The recruiter is supposed to know who wants what skills, and who has what needs. In that sense there is no difference from any other marketplace business.

- Regarding the thing you bring up: if they don't tell you the salary, stack, and team details, they have nothing and are just adding you to a database to be matched later. I responded to an advert during this last search where the guy admitted to not actually having a job. He'd just put up the ad with some keywords to attract people, and then the plan was to scan the firms to see if there was a match for me. I didn't proceed. I can appreciate you need to do this if you are a new recruiter, but it is indeed annoying.

- But the thing that is the most annoying is this: They will claim to put your CV forward for a role, and then do nothing. The reason is they may know the manager at firm A, B, and C. Firm D is also a likely destination for your profile, but he doesn't know them. So then they tell you that they will put your CV forward for A, B, C and D. This way you can't apply to firm D through another firm, and they are more likely to collect your placement fee. Sounds like an urban legend but a couple of people told me this in the last month, and sometimes it is indeed possible to find out from the inside whether your CV arrived.