Conciseness

The body is a lean, list-driven playbook that assumes Claude's competence, with only minor removable explanation of already-known concepts: "plant a property on Object.prototype and it appears on every object in the runtime" and "Poisoning Object.prototype doesn't do anything by itself — you need a gadget". It is efficient with minor over-explanation (anchor 4), not anchor 5, since the two framing paragraphs partly restate what Claude already knows.

Actionability

Fully executable, copy-paste-ready guidance throughout: the jq/npm dependency sweep ("jq '.dependencies,.devDependencies | to_entries[] ...'"), a concrete two-request curl PoC with exact JSON payload ("{'__proto__': {'shell': "/bin/bash", ...}}"), a negative-control payload ("same payload with 'proto' (no leading underscores)"), and concrete CVSS vectors with scores. Specific examples cover the common cases, matching anchor 5.

Workflow Clarity

Section 3 gives a clear 4-step numbered audit sequence (find merge call sites → trace user control → check fix version → check copy-path pollution), and validation exists (section 6 success signals plus a negative control), but validation is not integrated into the workflow sequence as an explicit checkpoint step. This matches anchor 4 (clear sequence, most checkpoints present, minor validation gaps) rather than 5, which would inline an explicit validate-and-recover loop into the workflow.

Progressive Disclosure

The skill is a single self-contained file with no bundle directories (no references/, scripts/, or assets/ exist), and the ~100-line body is organized into eight clearly numbered, scannable sections with no nested references and nothing that clearly needs splitting into a separate file. Per the judging guideline, a skill with no need for external references scores 5 with well-organized sections.

Specificity

The description names the domain precisely ("Hunt JavaScript prototype pollution (CWE-1321)") and one concrete action ("Hunt"), with chain outcomes "chains into RCE, auth bypass, and SSRF", but does not list several distinct concrete actions like auditing dependencies, building PoCs, or validating findings. It sits at anchor 3 (domain plus 1-2 concrete actions, not comprehensive) rather than 4, which requires several listed actions.

Completeness

The "what" is clear ("Hunt JavaScript prototype pollution ... chains into RCE, auth bypass, and SSRF"), but the description contains no "Use when..." clause or equivalent explicit trigger guidance — only a weak implication via "on most Node.js stacks". Per the judging guideline, a missing 'Use when...' clause caps completeness at 3; note that a keyword-string "when_to_use" exists in metadata but the description field itself lacks explicit trigger guidance, so this is not anchor 4.

Trigger Term Quality

Includes natural terms users would say: "JavaScript prototype pollution", "RCE", "auth bypass", "SSRF", "Node.js", plus the specific "CWE-1321". Missing common variations a user might naturally say such as "__proto__", "prototype chain", or "polluted object" in the description itself, matching anchor 4 (good keyword coverage, a few natural terms missing) rather than 5.

Distinctiveness Conflict Risk

"prototype pollution (CWE-1321)" carves out a highly specific niche that no generic document- or code-manipulation skill would claim, with distinct triggers. This matches anchor 5 (clear niche, minimal conflict risk); there is no meaningful overlap with adjacent skills beyond the intended one.