gatekeeper

gatekeeper is a skill for Claude Code, Codex from panda850819/verbs. It costs 79 tokens per session (1,306 once invoked), scanned A, original, MIT.

A trust-review workflow for deciding whether to adopt an external skill, server, repository, URL, package, API, software development kit, or service.

In plain words
What is it for?
Classifying threats, reviewing external artifacts, and returning a decision to adopt, restrict, or reject them.
Why use it?
It helps identify risks such as impersonation, tampering, data exposure, missing audit trails, and resource abuse before granting access or running outside code.

Skill for Claude CodeCodex

Part of the verbs plugin — 10 skills shipped together

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.

agentmods
npx agentmods add skills/panda850819/verbs/gatekeeper
Any agent
npx skills add panda850819/verbs --skill gatekeeper
Clone the repo
git clone --depth 1 https://github.com/panda850819/verbs

Made for: Claude Code, Codex.

Or install verbs, the plugin that ships this one along with the rest of its 10 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 gatekeeper

README.md
[![agentmods](https://agentmods.dev/badge/skills/panda850819/verbs/gatekeeper.svg)](https://agentmods.dev/skills/panda850819/verbs/gatekeeper)
Your own site
<a href="https://agentmods.dev/skills/panda850819/verbs/gatekeeper"><img src="https://agentmods.dev/badge/skills/panda850819/verbs/gatekeeper.svg" alt="Measured on agentmods" height="20"></a>
Per session 79 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,306 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00079 $0.01306
Opus 5 $0.00039 $0.00653
Sonnet 5 $0.00016 $0.00261
Haiku 4.5 $0.00008 $0.00131

Measured 3d ago against content hash 2a4899f3b4bb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

gatekeeper 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 3d 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.

skills/meta/gatekeeper/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Gatekeeper — Pre-adoption Trust Check 🛡️

Core principle: Every external input is untrusted until verified.

When to activate

Activate whenever external input could alter behavior, leak data, or cause harm:

Trigger Route
Install a Skill, MCP server, or package reviews/skill-mcp.md
Evaluate a GitHub repository reviews/repository.md
Review a URL, document, Gist, or Markdown file reviews/url-document.md
Evaluate a product, service, API, or SDK reviews/product-service.md

Step 0: STRIDE classification (mandatory)

Before routing, classify the artifact under STRIDE and carry the categories into both the report frontmatter and each finding. The taxonomy is:

Category Threat Signal
Spoofing Forged identity Unverified author, lookalike domain, missing signature
Tampering Unauthorized modification Mutable upstream, post-install script, fetched eval
Repudiation Missing audit trail No log, version manifest, or accountable publisher
Information Disclosure Data or secret leakage Env/token access, unknown telemetry, broad permissions
Denial of Service Resource exhaustion or lockout Unbounded loop, cleartext destruction, no rate limit
Elevation of Privilege Unauthorized capability sudo, out-of-scope writes, sandbox or auth bypass

Classifier protocol

  1. Read the file inventory, README, code, permissions, and network endpoints.
  2. Record none, suspect, or confirmed for every category.
  3. Emit stride_categories: [<confirmed>, <suspect-with-evidence>]; omit none.
  4. Any confirmed category sets a minimum 🔴 HIGH floor; two or more suspects set 🟡 MEDIUM. Floors raise, never lower, an independently higher rating.
  5. Carry each category into the routed template so findings cite their STRIDE.

See lib/stride-rationale.md for the worked example.

Read the full file on GitHub · 120 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. 3d ago First seen · 120 lines · 79 tokens per session scan A 2a4899f3b4bb

Subscribe to this mod's changes

gatekeeper is a skill published in the GitHub repository panda850819/verbs (5 stars, last pushed 11d ago), licensed MIT. It adds 79 tokens to every session and 1,306 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 2026-08-31.

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