vetting-agent-extensions

vetting-agent-extensions is a skill for Claude Code from trilwu/secskills. It costs 110 tokens per session (2,918 once invoked), scanned C, original, MIT.

A guide for deciding whether an AI coding-agent extension is safe to install. Extensions can include instruction files, configuration, and tool connections that the agent reads or runs.

In plain words
What is it for?
It helps review skill packs, plugins, MCP servers, startup configuration, environment files, and repositories before adding them to tools such as Claude Code, Cursor, or Cline.
Why use it?
A harmful extension may influence the agent as soon as it is loaded or started, so trusting it requires checking what it can make the agent do and access.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code; built for cline.

Part of the secskills-core plugin — 30 skills shipped together

Good fit It helps review skill packs, plugins, MCP servers, startup configuration, environment files, and repositories before adding them to tools such as Claude Code, Cursor, or Cline.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/trilwu/secskills/vetting-agent-extensions
Install

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.

Any agent
npx skills add trilwu/secskills --skill vetting-agent-extensions
Clone the repo
git clone --depth 1 https://github.com/trilwu/secskills

Made for: Claude Code.

Or install secskills-core, the plugin that ships this one along with the rest of its 30 skills.

Wrote 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.

agentmods badge for vetting-agent-extensions

README.md
[![agentmods](https://agentmods.dev/badge/skills/trilwu/secskills/vetting-agent-extensions/github.svg)](https://agentmods.dev/skills/trilwu/secskills/vetting-agent-extensions)
Your own site
<a href="https://agentmods.dev/skills/trilwu/secskills/vetting-agent-extensions"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/vetting-agent-extensions/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.

agentmods 80×15 button for vetting-agent-extensions

Your own site · 80×15
<a href="https://agentmods.dev/skills/trilwu/secskills/vetting-agent-extensions"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/vetting-agent-extensions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 110 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,918 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00110 $0.02918
Opus 5 $0.00055 $0.01459
Sonnet 5 $0.00022 $0.00584
Haiku 4.5 $0.00011 $0.00292

Measured 11d ago against content hash fcbc12338ff6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade C, and why

vetting-agent-extensions scanned grade C with 2 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 11d 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.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

runs it is a `curl | bash` with extra steps; the question is whether the

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

runs it is a `curl | bash` with extra steps; the question is whether the
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

secskills-core/skills/vetting-agent-extensions/SKILL.md · 238 lines

How it starts

The opening of the file, as written. The whole thing — 238 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Vetting Agent Extensions

An agent extension is not a library you call — it is text and configuration that your model reads as instructions and tooling your agent runs on your behalf. A malicious dependency has to wait for you to call it. A malicious skill is already in the context window, and a malicious MCP server may execute the moment the agent starts. The trust decision happens before either runs, and it is the decision this skill is about.

This is an adoption gate, not a code audit. The question is not "does this server have a CVE" — it is "if I install this, what can it make my agent do, and what can it read on its way out."

When to Use

  • Deciding whether to install a skill pack, plugin, or marketplace entry into Claude Code, Cursor, Cline, or a similar agent
  • Reviewing an MCP server before adding it to an agent's config — especially one that ships its own .mcp.json, .env, or startup wiring
  • Judging a repo that mixes skills, MCP config, and bootstrap scripts, where installing the repo wires all three at once
  • Assessing whether third-party agent content that gets loaded into context (skill bodies, tool descriptions, resources, bundled notes) can steer the model or leak the current engagement

When NOT to Use

  • Auditing an MCP server's own code for vulnerabilities — injection surfaces, tool scope, authz, transport — use auditing-mcp-servers. That skill reviews a server you are building or breaking; this one decides whether to trust one someone else built.
  • Dependency, package, lockfile, and CI/CD supply-chain risk — use auditing-supply-chain. An extension's npm/pip dependencies are its problem; route them there.
  • Prompt-injection and tool-abuse testing of an LLM application you are assessing — use securing-ai-systems.
  • Reviewing a diff to an extension you have already adopted — use reviewing-code-changes; come back here only if the diff changes what loads into context or what runs on startup.

Read the full file on GitHub · 238 lines

Changes

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.

  1. 11d ago First seen · 238 lines · 110 tokens per session scan C fcbc12338ff6

Subscribe to this mod's changes

vetting-agent-extensions is a skill published in the GitHub repository trilwu/secskills (138 stars, last pushed 6d ago), licensed MIT. It adds 110 tokens to every session and 2,918 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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