Agent Skills
Folders of instructions, scripts, and files that an agent loads only when the task calls for them, so the starting prompt stays small.
A skill is a folder with a description at the top. The agent reads only the descriptions until one of them matches the task; then it opens that folder and follows what is inside. Everything the skill needs — a checklist, a script, a template — travels with it.
The point is the context window. Instructions that sit in the prompt cost tokens on every turn, whether the task needs them or not. Instructions that sit in a skill cost a line of description until the moment they are used.
That also makes a skill a unit you can share. A team keeps its house rules in one folder instead of in everybody's prompt, and the rules change in one place.