Payflow MCP Server

A Model Context Protocol (MCP) server that provides tools for creating x402 payment headers to use with paid MCP servers. This server acts as a payment client, allowing users to generate payment headers that can be submitted to paid MCP tools.

Features

• Payment Creation: Generate x402 payment headers for USDC transactions on Base
• MCP Compatible: Works with any MCP client (Claude Desktop, etc.)

Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "payflow": {
      "command": "npx",
      "args": ["@chainbound/payflow-mcp"],
      "env": {
        "PRIVATE_KEY": "",
        // Set your max payment amount in USDC per tool call
        "MAX_PAYMENT_AMOUNT_USDC": "10",
      }
    }
  }
}

Installation

npm install -g @chainbound/payflow-mcp
# or
pnpm add -g @chainbound/payflow-mcp

Usage

Once connected, you can use the payment tool in Claude:

Create Payment

Generate a payment header for a paid MCP tool:

Create a payment of 0.05 USDC to 0x742d35Cc6634C0532925a3b8D1d3e14C1C3E6FC8 for the weather_forecast tool

This will return an x402 payment header that you can then use with paid MCP servers.

Tools

create_payment

Creates an x402 payment header for use with paid MCP tools.

Parameters:

• amount (number, required): Payment amount in USDC
• recipient (string, required): Ethereum address to receive the payment
• tool (string, optional): Name of the MCP tool being paid for

Returns:

• x402 payment header string that can be submitted to paid MCP tools

How It Works

1. Generate Payment: The tool creates a signed payment commitment using your private key
2. x402 Protocol: Uses the x402 micropayment protocol for blockchain payments
3. USDC on Base: All payments are in USDC on the Base network
4. Submit to Paid Tools: Use the generated header with paid MCP tools

Environment Variables

| Variable | Description | Required | |----------|-------------|----------| | PRIVATE_KEY | Your wallet private key (0x...) | ✅ | | MAX_PAYMENT_AMOUNT_USDC | Maximum payment amount in USDC | ✅ | | DEBUG | Set to payflow for debug logs | ❌ |

Security Notes

⚠️ Important Security Considerations:

• Your PRIVATE_KEY is used to sign payment commitments
• Keep your private key secure and never share it
• The private key should have USDC balance for payments
• Consider using a dedicated wallet for MCP payments

Development

# Install dependencies
pnpm install

# Run in development mode
pnpm dev

# Link the package to a local binary
pnpm link

# Build
pnpm build

# Start production server
pnpm start

Example Workflow

1. Start Payflow MCP: Run the server with your private key
2. Create Payment: Use the tool to generate payment headers
3. Use Paid Tools: Submit headers to paid MCP servers
4. Payment Settlement: Payments are automatically settled on Base

Related

• Payflow SDK - Build your own paid MCP servers
• x402 Protocol - Micropayment standard
• Model Context Protocol - MCP specification

License

MIT