heimdall

heimdall is a skill for Claude Code, Codex from caglarbozkurt/mcp-heimdall. It costs 71 tokens per session (610 once invoked), scanned A, original, MIT.

A security scanner for Model Context Protocol (MCP) servers, which let AI assistants connect to external tools and data.

In plain words
What is it for?
Reviewing a local server, npm or PyPI package, GitHub repository, or tools-list file before installing or connecting it.
Why use it?
It helps check an MCP server for prompt injection, data theft, malicious behavior, and—when requested—known dependency vulnerabilities.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Reviewing a local server, npm or PyPI package, GitHub repository, or tools-list file before installing or connecting it.

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

Made for: Claude Code, Codex.

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 heimdall

README.md
[![agentmods](https://agentmods.dev/badge/skills/caglarbozkurt/mcp-heimdall/skill/github.svg)](https://agentmods.dev/skills/caglarbozkurt/mcp-heimdall/skill)
Your own site
<a href="https://agentmods.dev/skills/caglarbozkurt/mcp-heimdall/skill"><img src="https://agentmods.dev/badge/skills/caglarbozkurt/mcp-heimdall/skill/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 heimdall

Your own site · 80×15
<a href="https://agentmods.dev/skills/caglarbozkurt/mcp-heimdall/skill"><img src="https://agentmods.dev/badge/skills/caglarbozkurt/mcp-heimdall/skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 610 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00071 $0.00610
Opus 5 $0.00036 $0.00305
Sonnet 5 $0.00014 $0.00122
Haiku 4.5 $0.00007 $0.00061

Measured 10d ago against content hash 2449c39be61c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

heimdall 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 10d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • heimdall — 100% identical, 0 lines differ
skill/SKILL.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Heimdall

Run a security scan on an MCP server and report the risk.

When to use

The user is about to install/connect an MCP server and wants to know if it's safe, or asks to "audit / scan / vet / check" an MCP, or pasted a tools/list output and asked whether the tool descriptions look poisoned.

How to run

From the Heimdall project directory:

# local server directory
npx tsx src/cli.ts <path-to-server>

# npm package, PyPI package (pypi:name), GitHub URL, or a tools/list JSON dump
npx tsx src/cli.ts <npm-package | pypi:name | github-url | tools.json>

# machine-readable
npx tsx src/cli.ts <target> --json

# also check the server's dependencies for known CVEs (queries OSV.dev over the network)
npx tsx src/cli.ts <target> --online

If installed globally / as a dependency, use heimdall <target> instead.

Add --online when the user wants supply-chain coverage: it checks declared dependencies against the OSV.dev advisory database and reports real CVE IDs. It sends only dependency names + versions (never source); leave it off to stay fully offline.

For a behavioral cross-check, heimdall validate <target> runs the server and calls its tools to observe what it actually does, then compares that to the static flags (confirmed / missed / not-exercised). It executes untrusted code with side effects — only suggest it in a disposable VM/container, never on the user's real machine.

To analyze injection with full fidelity when tool descriptions can't be read from source, capture the server's tools/list output to a file and pass --tools <file>.

Interpreting the result

  • verdict: pass / warn / fail. Any hard [GATE] finding forces fail.
  • risk score: 0 (clean) – 100 (worst).
  • fingerprint: stable hash of the tool surface. Save it; if it changes on a later scan, the MCP silently altered its tools (possible rug-pull).

Summarize the gates and highest-severity findings for the user, cite the evidence (file:line or tool:name), and give a clear install / don't-install recommendation. Never recommend installing a server with an unresolved GATE finding.

Read the full file on GitHub · 58 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. 10d ago First seen · 58 lines · 71 tokens per session scan A 2449c39be61c

Subscribe to this mod's changes

heimdall is a skill published in the GitHub repository caglarbozkurt/mcp-heimdall (0 stars, last pushed 2mo ago), licensed MIT. It adds 71 tokens to every session and 610 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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