When you vouch for someone, you’re lending them your name. Only lend it to people who’ll bring it back clean.

Vouching for somebody attaches your record to their behavior for as long as they are there. That is precisely why it means anything, because you are the one exposed if it goes badly, and that is what makes the recommendation worth hearing. Handing it out casually spends something that took years to build and restocks slowly. The person on the other end is trusting you, not them.

Only vouch where you have actually seen the work. Say clearly what you can speak to and what you cannot. If you do lend your name, tell the person plainly what they are carrying.