i see it as skills being logical grouping of a set of prompts, which achieve a goal. Like my optimize-critical-path skill.

It's more than a single prompt, but less than an entire agent. I find skills to be the tools you use on the fly. Like how I might have a wrench,screw-driver, hammer in my tool box.

tools vs skills is all about context efficiency from what I see. and yes, this isn't novel of claude. but they are the first to offer this abstraction.