Sometimes candidates send an inquiry to a recruiter without sending a cv, or including their phone number. We understand your wanting to be guarded up front, but if you want more information beyond the job posting, it is best done by a phone conversation. That way, you can get more info about the job, but also have a chance to ask questions, and to pick up on subtle nuances that aren’t apparent via email. At the same time, the recruiter can get to know you a bit better, and ask questions as well. Employers want to know a little about you beyond the cv, so this is a good time to accomplish that. It also helps the recruiter to see if the job is really right for you. For example if a candidate is looking for a new position to get a better quality of life and work less hours it helps to know that to weigh against what the employer needs and share that with the candidate.
If you still want to be guarded about sending your phone number so you aren’t inundated with unproductive calls from recruiters that really do not have anything to offer you, send your number along when a job posting is describing one particular position that captures your interest versus a blanket job post with the recruiter saying we have jobs, lots of jobs.