MCP Security Scanner

Audit any MCP server for tool-poisoning, prompt-injection, and data-exfiltration risk (OWASP LLM01 / LLM08) — before you connect an agent to it.

Live, agent-native, pay-per-scan over the x402 payment protocol on Base mainnet. No account, no API key, no subscription — an agent pays $0.05 USDC per scan inline and gets the report back in the same call.

Endpoint: https://x402-data-api.sigrunner.workers.dev/mcp MCP Registry: io.github.rezearcher/tech-risk

Why

Agents are wiring themselves to third-party MCP servers at runtime. A malicious or careless server can hide instructions in a tool description (tool-poisoning), smuggle a prompt-injection payload through a tool's output, or quietly exfiltrate data. These are the top of the OWASP LLM Top-10 (LLM01 prompt-injection, LLM08 excessive agency / supply-chain). There is no clean way for an agent to check the server it is about to trust on its own.

This tool is that check. Point it at an MCP server URL; it enumerates the server's tools and statically analyzes every tool schema for known poisoning / injection / exfiltration patterns, and returns a scored, itemized report.

Related MCP server: agent-audit

Tools

Discovery (tools/list) is free so agents can find the scanner. Two scan tools:

The free preview tells you whether a server is risky and how many issues. The paid scan tells you which tool is poisoned and how — the detail you need to actually act.

Both take a single argument:

{ "url": "https://target-mcp-server.example.com/mcp" }

Call it

BASE=https://x402-data-api.sigrunner.workers.dev

# discover (free)
curl -s -X POST $BASE/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

# free preview — counts + risk score, no payment
curl -s -X POST $BASE/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"scan_mcp_preview","arguments":{"url":"https://mcp.deepwiki.com/mcp"}}}'

# full scan — returns HTTP 402 with an x402 payment-required challenge until you attach payment
curl -i -X POST $BASE/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"scan_mcp_server","arguments":{"url":"https://mcp.deepwiki.com/mcp"}}}'

Any x402-capable client (e.g. the x402 libraries) handles the 402 → sign → retry automatically. Payment settles through the non-custodial xpay facilitator; no Coinbase/CDP account required.

What it detects

Static analysis of each advertised tool's name, description, and schema for:

• Tool poisoning — hidden/imperative instructions embedded in a tool description that try to steer the calling agent.

• Prompt injection — injection markers, role-override phrasing, and instruction smuggling.

• Data exfiltration — tool shapes that solicit secrets, credentials, or full context and ship them to an external sink.

• Invisible-unicode payloads — tag-block / zero-width characters used to hide instructions from a human reviewer.

• Dangerous capability — over-broad tool surface (shell, file, network) advertised without constraint.

Each hit carries a severity; the report rolls them into a 0–100 risk score.

Also included

Two enrichment tools on the same endpoint (tech-stack → CVE/EPSS/CISA-KEV risk, and domain firmographics) built on free/keyless sources (NVD, FIRST EPSS, CISA KEV, crt.sh, RDAP, Cloudflare DoH).

How it runs

A single Cloudflare Worker implements the MCP endpoint and the method-aware x402 gate: initialize and tools/list are free; tools/call on a paid tool returns HTTP 402 with a well-formed payment-required challenge until a valid X-PAYMENT proof is attached. Scan-target input is SSRF-guarded (internal/loopback/metadata addresses rejected).

License

MIT — see LICENSE.