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 GoldenWing-360/claude-security-skills --skill mcp-securitygit clone --depth 1 https://github.com/GoldenWing-360/claude-security-skillsWrote 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/goldenwing-360/claude-security-skills/mcp-security)<a href="https://agentmods.dev/skills/goldenwing-360/claude-security-skills/mcp-security"><img src="https://agentmods.dev/badge/skills/goldenwing-360/claude-security-skills/mcp-security/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/goldenwing-360/claude-security-skills/mcp-security"><img src="https://agentmods.dev/badge/skills/goldenwing-360/claude-security-skills/mcp-security.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00071 | $0.01914 |
| Opus 5 | $0.00036 | $0.00957 |
| Sonnet 5 | $0.00014 | $0.00383 |
| Haiku 4.5 | $0.00007 | $0.00191 |
Grade A, and why
mcp-security scanned grade A with 1 finding 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.
Reads agent configuration directorieslowAgent snooping
.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.
ls -la ~/.claude/mcp.json ~/.claude/settings.json 2>/dev/null Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
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.
MCP Security
The Model Context Protocol turns an LLM into a system that can act. That makes every MCP server a new piece of attack surface, with three properties that classical security tooling does not yet handle well:
- Capability creep — adding an MCP often adds dozens of tools at once. Most users never read what they granted.
- LLM as confused deputy — the LLM will happily call any tool that fits the conversational context, including ones the user did not mean to invoke.
- Cross-MCP attacks — one MCP can return data that triggers another MCP to act (indirect prompt injection across the tool boundary).
This skill is the audit/hardening counterpart to ai-agent-guardrails and prompt-injection-defense.
When to invoke
- A new MCP server is being installed
- An MCP advisory or version bump landed
- A contractor's or shared machine needs an audit
- An LLM agent made a write you did not expect — start here to scope what it could have done
- Periodic re-audit (monthly is reasonable for active stacks)
Step 1 — Inventory
MCP config can live in several places. Find them all.
# Claude Code / claude-desktop / cursor / windsurf — common locations
ls -la ~/.claude/mcp.json ~/.claude/settings.json 2>/dev/null
ls -la ~/Library/Application\ Support/Claude/claude_desktop_config.json 2>/dev/null
ls -la ~/.cursor/mcp.json ~/.codeium/windsurf/mcp_config.json 2>/dev/null
# Project-local MCPs
find ~/Code -maxdepth 3 -name '.mcp.json' -o -name 'mcp.json' 2>/dev/null
# Plugin-bundled MCPs (Claude Code plugin marketplace etc.)
ls -la ~/.claude/plugins/ 2>/dev/null
For each MCP you find, record: name, transport (stdio / http / sse), command or URL, scopes / API keys it holds, who installed it and when.
Step 2 — Risk-classify each MCP
Assign each MCP a tier. Re-do this whenever its capabilities change.
| Tier | Examples | What it means |
|---|---|---|
| 🟢 Read-only-local | filesystem with --readonly, sqlite read, jq |
Worst case: information disclosure of local files |
| 🟡 Read-only-remote | search APIs, read-only SaaS (status pages, dashboards) | Worst case: PII exfil via the LLM, query-quota burn |
| 🟠 Write-to-staging | dev-only DB, sandbox APIs (Stripe test, sandbox WP) | Worst case: corrupted staging data, recoverable |
| 🔴 Write-to-prod | hosting panel, prod DB, CMS, DNS, CI triggers | Worst case: customer impact, data loss, hard to undo |
| ⚫ Spend-money or send-on-behalf | payment APIs, email send, SMS, ad-budget changes | Worst case: financial loss, reputation damage, fraud |
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.
- 11d ago First seen · 140 lines · 71 tokens per session scan A e2614502fd6f
mcp-security is a skill published in the GitHub repository GoldenWing-360/claude-security-skills (17 stars, last pushed 1mo ago), licensed MIT. It adds 71 tokens to every session and 1,914 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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