Conciseness

The body is ~30 lean lines: a one-line goal ("Produce a single-page printable invoice"), a tight numbered layout spec, and a minimal output contract — every token earns its place and nothing explains concepts Claude already knows. This matches the 5 anchor ('lean and efficient; assumes Claude's competence'); it does not warrant 4 territory since there is no over-explanation to trim.

Actionability

Concrete structural guidance is present: exact table columns ("description / qty / unit / amount"), totals block fields ("subtotal, retainer, tax, total due"), and a literal artifact contract with type and title. It sits at 4 rather than 5 because details like the "Print stylesheet @media print to remove backgrounds" step are hints rather than executable code, and tax/retainer computation, currency formatting, and payment-instruction fields are left unspecified.

Workflow Clarity

The sequence (1. Read DESIGN.md → 2. Layout → 3. Print stylesheet → output contract) is clearly ordered, but step 1 points at a DESIGN.md that does not exist anywhere in the bundle (no references/, scripts/, or assets/ directories), so the workflow cannot be followed as written. That broken first step, plus no validation of the produced artifact (e.g., checking totals arithmetic or that all line items render), places it at the 3 anchor ('steps listed but gaps') rather than 4; this is not a destructive/batch operation, so the 3-cap rule is not the driver.

Progressive Disclosure

For a sub-50-line single-purpose skill the structure (## Workflow, ## Output contract) is well organized, but the body's only external reference — "Read DESIGN.md" — is dangling, and the frontmatter's design_system requirement implies a design reference that is absent. Per the guideline to score against the actual bundle structure, the broken reference prevents both the simple-skill 5 and the 4 anchor; it lands at 3 ('references present but' unusable / organization gaps that block navigation).

Specificity

"A printable invoice page — sender + recipient block, line items table, tax breakdown, totals, and payment instructions" enumerates several concrete deliverable components, matching the 'lists several specific actions; minor gaps' anchor. It falls short of 5 because it is a noun-phrase inventory of page parts rather than a comprehensive statement of actions performed, and it omits anything about styling/design-system application or the printable/print-orientation aspect beyond the adjective.

Completeness

It explicitly answers both what ("A printable invoice page — sender + recipient block, line items table, tax breakdown, totals, and payment instructions") and when ("Use when the brief mentions 'invoice', 'bill', 'billing statement', or '发票'") with concrete trigger phrases, which matches the 5 anchor almost verbatim. It is not 4 because the 'when' clause is fully explicit, not merely present-but-imprecise.

Trigger Term Quality

The triggers "invoice", "bill", "billing statement", "发票" are natural terms a user would actually say, giving good keyword coverage including bilingual synonyms — a fit for the 4 anchor. It is not 5 because common variations like "tax invoice", "statement of account", "账单" appears only in the triggers list and not the description body, and no file/format extensions are covered (though invoices have no canonical extension, coverage is still not exhaustive).

Distinctiveness Conflict Risk

The invoice domain is a clear niche with mostly distinct triggers, but the bare term "bill" is generic enough to fire on unrelated requests (e.g., a bill of materials, utility-bill parsing), which is exactly the 'minor overlap risk with closely related skills' situation of the 4 anchor. It is not 5 because of that "bill" ambiguity, and not 3 because the remaining triggers are unambiguous and domain-specific.