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 agentmods add skills/canonical/charm-tech/skill-scannernpx skills add canonical/charm-tech --skill skill-scannergit clone --depth 1 https://github.com/canonical/charm-techWrote 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/canonical/charm-tech/skill-scanner)<a href="https://agentmods.dev/skills/canonical/charm-tech/skill-scanner"><img src="https://agentmods.dev/badge/skills/canonical/charm-tech/skill-scanner.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00083 | $0.01921 |
| Opus 5 | $0.00042 | $0.00960 |
| Sonnet 5 | $0.00017 | $0.00384 |
| Haiku 4.5 | $0.00008 | $0.00192 |
Grade C, and why
skill-scanner scanned grade C with 3 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 4d 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.
Instruction-override phrasingmediumPrompt injection
Text telling the model to disregard its earlier instructions or safety rules is the shape of a prompt injection, whoever wrote it.
Evidence: "ignore all previous instructions" in the Output section. Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Downloads and executes remote codemediumSupply chain
curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.
- **Supply-chain risk** — unpinned dependencies, `curl | sh` install Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- **Supply-chain risk** — unpinned dependencies, `curl | sh` install How it starts
The opening of the file, as written. The whole thing — 203 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill Scanner
A security and quality review for SKILL.md files and their bundled
scripts, references, and assets. A skill becomes trusted content the
moment an agent loads it into context, so a poorly-authored or
malicious skill can silently degrade the agent or steer it around its
own guardrails. Run this scanner before installing a third-party skill,
before checking in a new skill, and in CI on every change.
This skill works in two tiers:
- Tier 1 — heuristic review (always): the checklist below. Fast, no execution, catches the common authoring and injection problems.
- Tier 2 — automated deep scan (when scripts/assets are present, or
when vetting an untrusted skill): run
scripts/scan_skill.pyand consult the deep-analysis references for script behaviour, secret exposure, supply-chain, and permission risk.
When to use
- You are vetting a skill before installing it from an external source.
- You just authored a new skill (after
skill-writer). - You edited an existing skill's body, scripts, or references.
- CI wants a pre-merge audit of changed skills.
Skip for drive-by typo fixes to an already-scanned skill, and for files that are never loaded into agent context (asset blobs, images).
Severity gating
Each finding carries HIGH / MEDIUM / LOW severity. Fix all HIGH
before merge or install; MEDIUM unless explicitly justified in the
skill; LOW at author discretion.
Tier 1 — heuristic checklist
1. Prompt-injection phrases
HIGH — text that would redirect the agent away from its system prompt. Scan for:
ignore (all )?previous instructionsdisregard (the |your )?(system|previous) (prompt|instructions)you are (now |actually )?a .* (assistant|agent|model)forget (everything|what you were told)new instructions:/new task:on its own line- Fenced blocks labelled "run this prompt" that contain the above.
Fix: rephrase without role assertion, or remove the block. Examples are
fine when clearly labelled as examples inside a fenced block — the test
is whether a bare reader could mistake the text for an instruction the
agent should follow. See references/prompt-injection-patterns.md for
the full pattern catalogue.
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.
- 4d ago First seen · 203 lines · 83 tokens per session scan C d6a5fd1edcb4
skill-scanner is a skill published in the GitHub repository canonical/charm-tech (2 stars, last pushed 18d ago), licensed Apache-2.0. It adds 83 tokens to every session and 1,921 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it C with 3 findings (instruction-override phrasing, downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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