Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add majiayu000/spellbook --skill npm-supply-chain-checkgit clone --depth 1 https://github.com/majiayu000/spellbookWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/majiayu000/spellbook/npm-supply-chain-check)<a href="https://agentmods.dev/skills/majiayu000/spellbook/npm-supply-chain-check"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/npm-supply-chain-check/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/majiayu000/spellbook/npm-supply-chain-check"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/npm-supply-chain-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00088 | $0.01294 |
| Opus 5 | $0.00044 | $0.00647 |
| Sonnet 5 | $0.00018 | $0.00259 |
| Haiku 4.5 | $0.00009 | $0.00129 |
Grade A, and why
npm-supply-chain-check scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 140 lines — stays where its author put it; the contents beside it link to each section on GitHub.
NPM Supply Chain Check
Run an evidence-bounded, read-only scan. Distinguish a dependency reference from proof that malicious code executed, and never read or print secret values.
Workflow
1. Fix the scan boundary
Resolve the exact repository or directory first. Default to the current repository only. Do not silently expand a repo scan to the user's home directory, all worktrees, global package caches, or CI systems.
2. Check intelligence freshness
Read references/shai-hulud-2026-iocs.json when investigating that incident.
It is a dated minimum baseline, not a complete list of every affected community
package. For an active incident, also check current primary sources such as the
npm registry and maintainer/security advisories before declaring a version safe.
Do not modify the bundled baseline during an ordinary scan.
3. Run the deterministic scanner
From this skill directory:
python3 scripts/scan_npm_supply_chain.py <target> --format text
Use JSON when another tool will consume the result:
python3 scripts/scan_npm_supply_chain.py <target> --format json
Add --deep only when source and built JavaScript files should also be searched
for network and campaign strings. Deep mode still reports paths and indicators,
not surrounding file contents.
Exit codes are machine-checkable:
0: scan completed and found no indicators in the checked scope.1: one or more affected versions or suspicious indicators were found.2: the scan could not complete because its target or IOC data was invalid.
4. Classify the evidence
| Evidence | Meaning |
|---|---|
| Affected version in a manifest or lockfile | Exposure candidate; it does not prove installation or execution. |
Affected version under node_modules |
Malicious package content may have been present locally. |
| Known malicious SHA-256 | High-confidence local artifact match. |
| IOC preinstall command or campaign/network string | Strong suspicious-content evidence; inspect provenance and timing. |
| IOC filename with a different hash | Triage lead only; filenames such as setup.mjs can be legitimate. |
| No findings | No known indicators in this scope and baseline; not proof of a clean machine. |
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 8d ago First seen · 140 lines · 88 tokens per session scan A ffe7b2dd9cce
npm-supply-chain-check is a skill published in the GitHub repository majiayu000/spellbook (278 stars, last pushed today), licensed MIT. It adds 88 tokens to every session and 1,294 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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