@certnode/mcp-sign

MCP server for CertNode AI Provenance. Sign AI-generated content with cryptographic receipts from Claude Desktop, Cursor, Windsurf, Claude Code, or any MCP-compatible client.

What it does

Exposes three tools to your AI client:

• sign_ai_output — sign AI-generated content. Returns a verifiable receipt with three-layer timestamps (CertNode internal + RFC 3161 independent TSA + Bitcoin anchor queued). Designed for admissibility under FRE 902.
• verify_signature — verify a CertNode signature. Free, no API key needed.
• get_receipt — fetch a previously-signed receipt by ID.

Install

npm install -g @certnode/mcp-sign

Or use via npx directly in your MCP config (no install needed).

Setup

1. Get an API key at https://certnode.io/ai-provenance (100 signings/month free, then $0.01/signing with volume discounts).

2. Add to your MCP client config:

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, or %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "certnode": {
      "command": "npx",
      "args": ["-y", "@certnode/mcp-sign"],
      "env": {
        "CERTNODE_API_KEY": "cn_live_..."
      }
    }
  }
}

Cursor (.cursor/mcp.json in your project or ~/.cursor/mcp.json):

{
  "mcpServers": {
    "certnode": {
      "command": "npx",
      "args": ["-y", "@certnode/mcp-sign"],
      "env": {
        "CERTNODE_API_KEY": "cn_live_..."
      }
    }
  }
}

Claude Code — add via command line:

claude mcp add certnode npx -- -y @certnode/mcp-sign
# then set CERTNODE_API_KEY in your environment

3. Restart your MCP client. The sign_ai_output, verify_signature, and get_receipt tools are now available.

Usage

Ask your AI:

"Generate a marketing email for our Q2 product launch, then sign it with CertNode provenance so we have proof of creation time and source model."

The AI will:

1. Generate the email.
2. Call sign_ai_output with the content + model metadata.
3. Return the email plus a verifiable receipt ID.

Store the receipt ID with your content. When a customer disputes authenticity or a regulator asks for compliance proof, you have cryptographic evidence.

Verification

Anyone (not just you) can verify a signature at https://certnode.io/verify/[receiptId]. No account or API key required for verification.

Pricing

| Monthly volume | Per-signing | |---|---| | 0 – 100 | Free | | 100 – 10,000 | $0.010 | | 10,000 – 100,000 | $0.007 | | 100,000 – 1,000,000 | $0.004 | | 1,000,000+ | $0.002 |

Volume discounts apply automatically. Verifications are always free. No subscription required.

Environment variables

| Variable | Required | Default | Description | |---|---|---|---| | CERTNODE_API_KEY | yes | — | Your API key (cn_live_... or cn_test_...) | | CERTNODE_API_BASE | no | https://certnode.io/api/v1/provenance | Override for self-hosted or staging |

Troubleshooting

"CERTNODE_API_KEY environment variable not set" The MCP client didn't pass the env var. Check your client config.

"invalid_or_revoked_api_key" The key was revoked in the dashboard. Generate a new one at https://certnode.io/dashboard/provenance.

"free_tier_exceeded" You've hit 100 signings this month without a paid subscription. Add a payment method at https://certnode.io/dashboard/provenance/billing.

Links

• Homepage: https://certnode.io/ai-provenance
• Docs: https://certnode.io/ai-provenance/docs
• Source: https://github.com/srbryant86/certnode/tree/main/packages/mcp-sign
• License: MIT