So this is the tap I have and I’d like to attach an accessory to it. I believe it is threaded and I should be able to unscrew the existing head to be able to use the threads, but I don’t know how to remove it. The plier (correct word?) tool that I have has sharp teeth and it’s scratching and damaging the tap. I’ve tried several grippy, nonslip layers between them to avoid damage but it’s still slipping or scratching the tap. Any suggestions?
I will use a piece of leather if I don't want to damage the finish. Think old leather belt if you don't have any scraps of leather.
The curving spigot probably is a press fit and would not unscrew from the valve body. Afik all valve bodies of this type are removed from below. You or an assistant holds the valve body (the part you can see above the lavatory) with a hand and you use a "basin wrench" to remove a nut from below.
Sometimes the threads are internal, as in female. Have a look at the water screen(also called an aerator) and see if you can unscrew it.