It's really contextual honestly. If someone you're talking to is very puzzled by your inability to speak, then disclosing it actually eases the air of the conversation and their facial expression softens in understanding. You'd be surprised how many people have never heard someone stutter. Or if your speech is really tanking and you're getting worse and worse, a brief mention that you stutter can actually improve your state psychologically. You're essentially setting the frame of the conversation that your stutter is socially acceptable. This scenario works when you're very tight in your body and your vocal chords are freezing up and is more for your benefit than theirs. But 98% of the time I don't mention that I stutter. Honestly try it out and see what works for you