Lookproof MCP server

An MCP server that gives Claude and other AI agents 23 Lookproof tools: domain and site health, SPF, DKIM, DMARC, MTA-STS, BIMI, DNS, DNSSEC, CAA, RDAP, TLS certificates and HTTP security headers. The agent pays per call in USDC on Base via x402, from a wallet you control, with a spending cap per session.

Every tool description states its price, so the agent can see what a call costs before making it. Without X402_PAY=1 nothing is ever paid: every tool is a dry run that reports the price and returns no data.

uvx lookproof-mcp --version     # needs uv: https://docs.astral.sh/uv/

Tools

get_spending is free and shows what the session has spent and how much budget is left.

Endpoints without a tool

Lookproof has 47 paid endpoints. This server exposes the 23 an agent is most likely to need for questions about a domain's DNS and mail security, because every extra tool costs context and makes the agent's choice harder. The other 24, and why they are left out:

All of them are in docs/endpoints.md. To add one, copy a tool in src/lookproof_mcp/server.py, set its path and price, and run uv run lookproof-mcp --check.

Setup

Use a dedicated wallet with a few dollars of USDC on Base mainnet. Never your main wallet.

Store the wallet key in a file only you can read, so it never sits in an MCP client's config file:

install -m 600 /dev/null ~/.lookproof-wallet.key
nano ~/.lookproof-wallet.key        # paste the private key, save

The server runs with uv's uvx, which downloads lookproof-mcp from PyPI into its own environment, with exactly the dependency versions this release was tested with. There is nothing to clone or install by hand. Try it without a wallet first: with no settings, every tool is a dry run.

Settings

How payments are limited is described under Security.

Claude Code

claude mcp add lookproof \
  --env X402_PAY=1 \
  --env PRIVATE_KEY_FILE=$HOME/.lookproof-wallet.key \
  --env MAX_SPEND_USD=0.25 \
  -- uvx lookproof-mcp

Leave out --env X402_PAY=1 to try it as a dry run first.

Then ask, for example: "Is example.com protected against email spoofing? Check SPF, DMARC and MTA-STS."

Claude Desktop

Add this to claude_desktop_config.json (Settings, Developer, Edit Config) and restart Claude Desktop:

{
  "mcpServers": {
    "lookproof": {
      "command": "uvx",
      "args": ["lookproof-mcp"],
      "env": {
        "X402_PAY": "1",
        "PRIVATE_KEY_FILE": "/home/you/.lookproof-wallet.key",
        "MAX_SPEND_USD": "0.25"
      }
    }
  }
}

If Claude Desktop can't find uvx, use its full path (which uvx on macOS and Linux, where uvx on Windows). On Windows, write the key path as C:\\Users\\you\\.lookproof-wallet.key.

What a tool call returns

Paid (shape only, not yet verified against the live API; data is the full Lookproof response):

{
  "data": {"endpoint": "mail.dmarc", "status": "<ok|info|warning|error|unknown>", "data": {"policy": "...", "...": "..."}, "findings": ["..."]},
  "cost_usd": 0.01,
  "session_spent_usd": 0.01,
  "session_remaining_usd": 0.09,
  "tx": "https://basescan.org/tx/0x<transaction-hash>"
}

Dry run (no X402_PAY=1):

{"dry_run": true, "would_cost_usd": 0.08, "network": "eip155:8453", "pay_to": "0x<lookproof-address>",
 "note": "Dry run, nothing paid and no data. The user can set X402_PAY=1 to enable payments."}

When the cap is reached:

{"error": "Session spending cap reached: $0.090 spent of MAX_SPEND_USD=$0.1; this call costs $0.080. Restart the server or raise MAX_SPEND_USD."}

Security

• Dedicated wallet. Use a wallet that only holds what you are willing to spend on checks, never your main wallet. Prefer PRIVATE_KEY_FILE over PRIVATE_KEY, so the key is not in the MCP client's config file; the server refuses a key file that other users can read.
• Dry run by default. Nothing is signed or paid unless X402_PAY=1 is set.
• Spending cap. MAX_SPEND_USD (default $0.10) caps what one server process can spend. The cost of a call is reserved before paying, so parallel calls cannot overshoot it, and a call that fails after the payment was signed stays counted and is reported as "possibly paid".
• Price check. A tool refuses to pay more than the price in its description.
• Locked payment. Each payment is locked to the amount, asset (USDC), network (Base, eip155:8453) and payTo address of the 402 the server just received for that call. If the second 402 asks for anything else, nothing is signed. With PAYTO_ALLOWLIST, a payTo outside the list is refused before signing.
• Results are data. Tool results contain records and web content published by the checked domain's owner. The agent is told to treat them as data, and the cap and price checks apply whatever it is told.
• Identifiable client. Every request carries User-Agent: lookproof-mcp/<version>.

Command line

Run from source

git clone https://github.com/lookproof/x402-examples.git
cd x402-examples/mcp-server
uv run lookproof-mcp            # or: uv run lookproof-mcp --check

Source, issues and the other x402 examples (quickstart, domain monitor): github.com/lookproof/x402-examples.