security-pass

security-pass is a skill for Claude Code from cyanheads/toolkit-mcp-server. It costs 118 tokens per session (5,026 once invoked), scanned A, a copy of security-pass, Apache-2.0.

A security review workflow for MCP servers, which provide tools and data that an agent can call. It checks the server's inputs, permissions, data handling, and error behavior.

In plain words
What is it for?
Use it before a release, after changing handlers or services, or during a periodic review. It covers tool and prompt descriptions, destructive actions, authentication, paths, URLs, shell use, validation, tenant separation, and error leakage.
Why use it?
It helps find ways an agent, user input, or upstream service could cause unwanted actions, expose information, or cross user boundaries.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the toolkit-mcp-server plugin — 32 skills, 1 MCP server shipped together

Good fit Use it before a release, after changing handlers or services, or during…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cyanheads/toolkit-mcp-server/security-pass
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 cyanheads/toolkit-mcp-server --skill security-pass
Clone the repo
git clone --depth 1 https://github.com/cyanheads/toolkit-mcp-server

Made for: Claude Code.

Or install toolkit-mcp-server, the plugin that ships this one along with the rest of its 32 skills, 1 MCP server.

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 security-pass

README.md
[![agentmods](https://agentmods.dev/badge/skills/cyanheads/toolkit-mcp-server/security-pass.svg)](https://agentmods.dev/skills/cyanheads/toolkit-mcp-server/security-pass)
Your own site
<a href="https://agentmods.dev/skills/cyanheads/toolkit-mcp-server/security-pass"><img src="https://agentmods.dev/badge/skills/cyanheads/toolkit-mcp-server/security-pass.svg" alt="Measured on agentmods" height="20"></a>
Per session 118 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,026 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod 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 $0.00118 $0.05026
Opus 5 $0.00059 $0.02513
Sonnet 5 $0.00024 $0.01005
Haiku 4.5 $0.00012 $0.00503

Measured 7d ago against content hash bdcf2da08d1c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

security-pass scanned grade A 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 7d 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.

Makes network callslowCapability

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

**Smell:** `return { body: await fetch(url).then(r => r.text()) }` rendered directly in `format()`. Or: `description: \`Look up ${tenant.customLabel}\`` where `customLabel` is tenant-supplied.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

grep -rnE "\b(exec|spawn|execSync|spawnSync)\b" src/
Origin

This is a copy

100% identical to security-pass — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/security-pass/SKILL.md · 347 lines

How it starts

The opening of the file, as written. The whole thing — 347 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Context

An MCP server is a new attack surface with unique properties — tool output feeds back into the LLM's context, scopes gate what the model can do on the user's behalf, and per-request state must stay tenant-scoped. This skill walks a server through eight axes shaped around what the server builder actually controls. Framework-level concerns (transport, JSON-RPC parsing, auto-correlation, error classification) are out of scope — mcp-ts-core handles those.

Read the code. Don't trust patterns from memory.

When to Use

  • Before a release
  • After adding or modifying a batch of handlers or services
  • Periodically (quarterly-ish)
  • User asks for a "security review", "audit", "hardening pass", or similar

Inputs

Gather before starting. Ask if unclear:

  1. Scope — whole server, specific module, or recent diff?
  2. Known concerns — anything the user already suspects?
  3. Deployment context — multi-tenant? public network? auth mode? (stdio / local-http / public-http behave differently)
  4. Severity floor — report all findings, or skip medium/low?

Steps

1. Build the map

Surface what you're auditing before diving in. Paths below assume the mcp-ts-core layout — adjust to your repo.

find src/mcp-server/tools/definitions -name "*.tool.ts" | sort
find src/mcp-server/resources/definitions -name "*.resource.ts" 2>/dev/null | sort
find src/mcp-server/prompts/definitions -name "*.prompt.ts" 2>/dev/null | sort
find src/services -maxdepth 1 -mindepth 1 -type d | sort

Note: tool / resource / prompt counts, auth mode, storage provider, upstream APIs, which tools have destructiveHint, which handlers request a consent round via ctx.requestInput, which services hold module-scope state, whether the server reads roots.

If transport is streamable HTTP or SSE, also capture:

  • Bind address (127.0.0.1 for local, or 0.0.0.0 / public interface?)
  • Origin allowlist (DNS rebinding mitigation) — configured, or wildcard / missing?
  • Session ID source (framework CSPRNG, or builder-supplied?) and binding to auth identity
  • Any unauthenticated routes (/healthz, /sse, metadata endpoints) — do they leak tool lists or tenant hints?
  • MCP Authorization spec: if implemented, PKCE enforced, token audience (aud) checked, resource indicators used

Read the full file on GitHub · 347 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. 7d ago First seen · 347 lines · 118 tokens per session scan A bdcf2da08d1c

Subscribe to this mod's changes

security-pass is a skill published in the GitHub repository cyanheads/toolkit-mcp-server (18 stars, last pushed 15d ago), licensed Apache-2.0. It adds 118 tokens to every session and 5,026 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). It is 100% identical to security-pass, differing in 0 lines, and is treated as a copy.

Related

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