What comes out
A complete skill file: valid YAML frontmatter, a description written as a condition rather than a title, trigger phrases in the words a user would actually type, and a body of numbered steps and rules.
The token readout splits the two halves, because they have different economics. The description sits in context on every request whether or not the skill fires; the body loads only when it does.
The description is the whole skill
This is the mistake that makes skills fail, and it fails silently — a skill with a vague description simply never triggers, and you conclude the mechanism does not work.
Weak: “A tool for reviewing prompts.” Describes what it is. Matches almost nothing, because users do not phrase requests that way.
Strong: “Use when the user asks to review, critique or improve a prompt, or asks what is wrong with one.” Describes when, in the words someone would type.
Every blueprint here writes the description in the second form and generates triggers to match.
The three shapes
Review applies fixed criteria to something the user already has. Its defining rule is that every finding must quote the text it refers to, which stops the output becoming a list of opinions.
Generate produces an artefact to a house standard. The body is a checklist the model applies rather than instructions it interprets, which is what makes output consistent between runs.
Diagnose works causes in order of likelihood. This is the highest-value shape, because the alternative is the model guessing — and ordering by likelihood is what makes it faster than the user searching themselves.
When something belongs in a skill
The rule is about frequency, not importance. Anything needed on most requests belongs in the system prompt. Anything needed occasionally belongs in a skill, where its body is paid for only when it triggers.
Teams get this backwards constantly, because the system prompt is the obvious place to put a fix. The prompt splitter finds the conditional sections in a prompt you already have and shows what extracting them would save.
After you generate
Open it in the skill builder to edit with live validation, and save it to your library. If the body runs past roughly three thousand tokens, it is usually two skills — splitting means the model loads only the half it needs.