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 ScopeBlind/scopeblind-gateway --skill protect-mcpgit clone --depth 1 https://github.com/ScopeBlind/scopeblind-gatewayWrote 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/scopeblind/scopeblind-gateway/protect-mcp)<a href="https://agentmods.dev/skills/scopeblind/scopeblind-gateway/protect-mcp"><img src="https://agentmods.dev/badge/skills/scopeblind/scopeblind-gateway/protect-mcp/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/scopeblind/scopeblind-gateway/protect-mcp"><img src="https://agentmods.dev/badge/skills/scopeblind/scopeblind-gateway/protect-mcp.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 | $0.00040 | $0.00631 |
| Opus 5 | $0.00020 | $0.00316 |
| Sonnet 5 | $0.00008 | $0.00126 |
| Haiku 4.5 | $0.00004 | $0.00063 |
Grade C, and why
protect-mcp scanned grade C 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.
Recursive force deletehighDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
context.input.command like "rm -rf *" What it actually says
protect-mcp — Agent Governance with Cryptographic Receipts
What This Does
Adds two layers to every tool call:
- Cedar policy enforcement — evaluate allow/deny decisions using the same
authorization engine AWS uses for IAM. Policies are declarative
.cedarfiles. - Ed25519 receipt signing — each tool call produces a tamper-evident receipt. If the record is modified after signing, the signature breaks. Anyone can verify offline without trusting the issuer.
Setup
# One-time: configure Claude Code hooks
npx [email protected] init-hooks
# Start the hook server (runs on port 9377)
npx [email protected] serve --enforce
This configures Claude Code to POST every tool call event to protect-mcp for policy evaluation and receipt signing. First run auto-generates permissive Cedar policies that you can tighten.
Usage
Once running, protect-mcp operates silently. Every tool call:
- Is evaluated against Cedar policies (allow/deny/ask)
- Produces a signed receipt in
.protect-mcp-log.jsonl - Decision is returned to Claude Code within ~1ms
Verify Receipts
# Verify all receipts in the log
npx @veritasacta/verify .protect-mcp-log.jsonl
# Verify a single receipt
npx @veritasacta/verify receipt.json
What a Receipt Looks Like
{
"type": "protectmcp:decision",
"tool_name": "Bash",
"decision": "allow",
"policy_digest": "sha256:a3f8...",
"issued_at": "2026-04-04T12:00:00Z",
"signature": { "alg": "EdDSA", "sig": "..." }
}
Cedar Policy Example
// Block destructive commands
forbid (
principal,
action == Action::"tool_call",
resource == Tool::"Bash"
) when {
context.input.command like "rm -rf *"
};
Links
- npm: https://npmjs.com/package/protect-mcp
- Source: https://github.com/scopeblind/scopeblind-gateway
- IETF Draft: https://datatracker.ietf.org/doc/draft-farley-acta-signed-receipts/
- Merged into Microsoft Agent Governance Toolkit (PR #667)
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 · 89 lines · 40 tokens per session scan C 3982a6ea0787
protect-mcp is a skill published in the GitHub repository ScopeBlind/scopeblind-gateway (9 stars, last pushed today), licensed MIT. It adds 40 tokens to every session and 631 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 1 finding (recursive force delete). It comes from a forked repository.
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