Conciseness

The body stays lean — task tables instead of prose, no explanations of concepts Claude already knows (no "what is a webhook" padding) — but the instruction to read bundled files before working is repeated across the intro ("A link or filename in this skill isn't a substitute for reading its contents"), the implementation-guidance section, and step 1 of the load procedure. That matches anchor 4 (efficient with minor trims possible) rather than anchor 5's every-token-earns-its-place.

Actionability

Most guidance is concretely executable for an instruction-only router skill: exact per-task file paths (<references/script-extensions.md>, <references/backend.md>), load ordering ("then the selected extension point's implementation guide"), and path-resolution rules. A few rows remain high-level ("Follow the selected interface's product documentation from the extension-point catalog"; "Customize another product's behavior"), which keeps it at anchor 4 rather than 5.

Workflow Clarity

The three-step load sequence (select from tables, follow in-file pointers, read canonical docs) is clearly ordered, and checkpoints exist ("If the documentation doesn't establish that an extension meets a requirement, state what is unknown or unsupported before proceeding"; "Report the changes, validation results, and remaining steps"). Validation specifics (testing, build verification) are deferred to references/workflow.md rather than stated as explicit checkpoints here, matching anchor 4 over anchor 5.

Progressive Disclosure

SKILL.md is a clean overview that inlines nothing which belongs in separate files; all twelve cited references/*.md files exist, carry real content, and are one level deep, clearly signaled via task tables. Sibling cross-pointers (e.g. backend.md → webhooks.md) are explicitly managed by the skill's step 2 ("Use this skill's direct links to locate those files"), so navigation is easy with no buried content chains — matching anchor 5.

Specificity

"Build, modify, or review Stripe Apps and extensions" names several concrete actions tied to specific artifacts (stripe-app.yaml, @stripe/ui-extension-sdk, @stripe/extensibility-sdk, script extensions, custom workflow actions), but actions the skill actually covers — scaffolding, testing, publishing, debugging — are absent, leaving minor coverage gaps. It sits above anchor 3 (only 1-2 concrete actions) and below anchor 5 (comprehensive action coverage).

Completeness

The description explicitly answers both: what ("Build, modify, or review Stripe Apps and extensions using the relevant documentation and reference guides") and when ("Use for custom Stripe Dashboard UI, stripe-app.yaml... Also use when deciding whether a Stripe extension can support the user's billing or workflow requirements") with concrete trigger phrases. This clearly matches the anchor-5 example pattern rather than anchor 4's weaker 'when' clause.

Trigger Term Quality

Natural developer phrasing is well covered ("Stripe Apps", "custom Stripe Dashboard UI", "script extensions", "custom workflow actions", plus the manifest filename and SDK package names), yet a few terms users would plausibly say — "webhooks" (only implied by "react to events"), "marketplace", "scaffold" — are missing. This matches anchor 4 (good coverage, a few natural terms missing) rather than anchor 5's comprehensive synonym coverage.

Distinctiveness Conflict Risk

The description carves out a clear niche — Stripe Apps/extensions specifically — anchored by distinct triggers like the manifest file and SDK package names, so it is unlikely to fire for unrelated skills. The broadened billing/workflow clause is qualified by "Stripe extension", keeping conflict risk minimal and matching anchor 5 rather than anchor 4's minor-overlap case.