Conciseness

The body is dense with actionable content — code, tables, and checklists rather than concept explanations — with only minor trimming opportunities, e.g. the vendor-payload guidance repeated in Step 3 and Step 7, and the Overview's background sentence about the spec "formaliz[ing] the signing, retry, and replay patterns most production systems converged on". Not a 5 because of that duplication and light background padding; not a 3 because nearly every section carries task-specific value Claude could not infer.

Actionability

Concrete, mostly executable Python test code with explicit assertions throughout (e.g. the sign_webhook helper and signature/replay tests), and the anti-patterns table gives specific fixes. Not a 5 because a few snippets have gaps: `headers=...` is elided in Step 6, `SECRET`/`time` are used before import, and `capture_outbound_webhook`/`mock_receiver` are undefined helpers — minor gaps that keep it from copy-paste ready.

Workflow Clarity

Steps 1–9 are clearly sequenced (sender then receiver, building from payload shape to end-to-end), each step carries explicit assertions as validation, and Step 9 provides a checklist for both sides. Failure handling is explicit — "If receiver doesn't enforce this, mark **critical**: replay vulnerable" and "If your handler can't survive out-of-order, mark **critical**" — giving feedback loops for error recovery. Not a 4 because checkpoints and failure outcomes are explicit, not implicit.

Progressive Disclosure

The body is a well-organized overview that keeps core workflow code inline and pushes lookup tables and vendor links to references/vendor-payloads-and-retries.md and advanced attack cases (tamper, future-timestamp, key rotation, capture sanitization) to references/inbound-replay.md — both real files, one level deep, clearly signaled in context and again in a References section, with no nested references inside them. Not a 4 because the split is clean, navigation is easy, and nothing that belongs in a reference file is inlined.

Specificity

The description enumerates many concrete capabilities: "HMAC-SHA256 signatures, retries with backoff and jitter, timestamp replay windows, ordering, dead letters and body encoding per Standard Webhooks, plus replaying captured inbound payloads with tampering and key rotation cases" — comprehensive coverage of concrete actions, matching the anchor's example of multiple specific actions. Not a 4 because coverage spans both sending and receiving sides with no meaningful gaps.

Completeness

Both questions are explicitly answered: what — testing signatures, retries, replay windows, ordering, dead letters, encoding, and payload replay with tampering/key rotation; when — "Use whenever webhooks need tests, on the sending or receiving side", an explicit trigger clause with concrete conditions. Not a 4 because the 'when' clause is explicit and specific rather than merely present.

Trigger Term Quality

Good natural keyword coverage — "webhooks", "tests", "signatures", "retries", "replay" are terms users would say when needing this skill. Not a 5 because common synonyms like "callbacks", "endpoints", or "delivery failures" are absent; not a 3 because the present keywords are specific and naturally phrased rather than generic.

Distinctiveness Conflict Risk

"webhook-delivery-tester" carves a clear niche — webhook delivery testing on both sender and receiver sides per Standard Webhooks — with distinct triggers unlikely to fire for generic HTTP-testing or idempotency skills. Not a 4 because the trigger terms (webhooks, signatures, retries, replay) are unambiguous and don't overlap with neighboring skills' vocabulary.