Ah not exactly.

The way the OP phrased it

> Is a skill essentially a reusable prompt that is inserted at the start of any query?

Actually is a more apt description for a different Claude Code feature called Slash Commands

Where I can create a preset "prompt" and call it with /name-of-my-prompt $ARGS

and this feature is the one that essentially prefixes a Prompt.

The other description of lazy loading is more accurate for Skills.

Where I can tell my Claude Code system: Hey if you need to run our dev server see my-dev-server-skill

and the agent will determine when to pull in that skill if it needs it.