This skill is a pointer. The bar for "best" is your own principles, wherever you keep them (a principles file in your constitution, your AGENTS.md, a values note). The skill adds no criteria of its own; it routes recent work back through yours. If you have none written down, the model uses the plainest general standard for that kind of work (correct, simple, clear, and finished) and says so.
Look at what was just created or changed. One question. Is this the best possible version of itself?
Re-read the principles. Anything that violates them isn't finished. Beyond that, "optimal" depends on what you're looking at (code, copy, architecture, or design), so decide what to examine and how deep to go.
Fix what you find. If it's a taste call only you can make, flag it instead of deciding it.
After fixing, say what changed and why, briefly. If nothing needs fixing, say "clean" and nothing else.
The bar is simple. If you asked "would you change anything?", the honest answer is no.