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PQSafe PQSafe AgentPay

MCP Adapter

The MCP adapter exposes PQSafe payment capabilities as a Model Context Protocol tool. Any MCP host (Claude Desktop, Claude Code, or any MCP-compatible runtime) can authorize and dispatch payments without needing to import the SDK directly.

What is MCP?

MCP (Model Context Protocol) is Anthropic’s open standard for connecting AI models to external tools and services. The PQSafe MCP server exposes a pqsafe_pay tool that any MCP host can call.

MCP server setup

The PQSafe MCP server lives in ~/Projects/pqsafe/mcp-server/. To run it:

Terminal window
cd ~/Projects/pqsafe/mcp-server
npm install
npm run build

Add to your MCP host config (e.g., Claude Desktop ~/.claude/settings.json):

{
  "mcpServers": {
    "pqsafe": {
      "command": "node",
      "args": ["/path/to/pqsafe/mcp-server/dist/index.js"],
      "env": {
        "PQSAFE_ISSUER_KEY": "pk_live_...",
        "PQSAFE_DEFAULT_RAIL": "airwallex",
        "AIRWALLEX_CLIENT_ID": "...",
        "AIRWALLEX_API_KEY": "..."
      }
    }
  }
}

Tool schema

Once connected, the MCP host sees this tool:

{
  "name": "pqsafe_pay",
  "description": "Execute a post-quantum-authorized payment via PQSafe AgentPay. Payments are bounded by the active spend envelope — amount, recipient, and rail are all cryptographically enforced.",
  "inputSchema": {
    "type": "object",
    "properties": {
      "recipient": {
        "type": "string",
        "description": "Payment recipient domain or address (must be in envelope allowlist)"
      },
      "amount": {
        "type": "number",
        "description": "Payment amount in envelope currency (must be ≤ envelope maxAmount)"
      },
      "memo": {
        "type": "string",
        "description": "Payment memo — appears in ledger and bank statement"
      },
      "rail": {
        "type": "string",
        "enum": ["airwallex", "wise", "stripe", "usdc-base", "x402"],
        "description": "Payment rail (must be in envelope allowedRails)"
      }
    },
    "required": ["recipient", "amount", "memo"]
  }
}

Envelope management via MCP

The MCP server also exposes envelope management tools:

ToolDescription
pqsafe_create_envelopeCreate and sign a new spend envelope
pqsafe_revoke_envelopeRevoke an envelope by ID
pqsafe_check_envelopeInspect the current envelope bounds
pqsafe_get_ledgerRetrieve recent ledger entries

Example MCP session

User: Pay the Cloudflare invoice for $47.50


Claude: I'll use PQSafe to pay the Cloudflare invoice.


[Calling pqsafe_pay]
  recipient: "cloudflare.com"
  amount: 47.50
  memo: "Cloudflare invoice — April 2026"
  rail: "stripe"


[Tool result]
  status: "settled"
  txId: "txn_stripe_ch_3Qx..."
  ledgerHash: "0xa3f9c2..."


The Cloudflare invoice for $47.50 has been paid successfully.
Transaction ID: txn_stripe_ch_3Qx...
The payment has been recorded in the PQSafe ledger.

Security model

The MCP adapter inherits all PQSafe envelope guarantees:

  • The envelope is created and signed at server startup (not per-request)
  • The MCP server validates all tool calls against the active envelope before dispatching
  • The envelope’s allowedRecipients, maxAmount, and allowedRails cannot be overridden via MCP
  • The host agent (Claude) can only call what the envelope permits

Next steps