A skill is the difference between explaining the same task from scratch every time and giving the agent a written way to do it again. Most skills are just text, often a markdown file. We explain it as close to a prompt but more durable: a prompt is what you say right now, a skill is what you save because you’ll need it again.
The best client frame is a recipe. You cook the meal once, write down the process, then reuse it with different ingredients. The recipe stays stable. The ingredients change: the client files, transcripts, and examples you give the agent for this run.
How it shows up
In Claude Code, Codex, or another agent tool, a skill might handle transcript processing, code review, document cleanup, or client email drafting. Skills sit between project instructions and a full application: project instructions are the standing rules for the whole project, a skill teaches one repeatable workflow. If work is fully deterministic and needs no judgment, you may want a script instead. One of our CPA clients got tangled with five different journal-entry skills. The better question is which part is the reusable workflow and which part is context, not how many copies to keep.
Why you care
Build skills from real work: do the task manually with the agent, correct it, run it again with variation, then have the agent turn the pattern into a skill and test it before sharing. One caution, since skills are shareable files: a bad rule inside a skill carries bad instructions, so treat an outside skill like a procedure someone handed your team. A skill lets good work compound instead of getting re-explained every time.