MCPay SDK & CLI

A TypeScript SDK and CLI for connecting to MCP (Model Context Protocol) servers with payment capabilities via the x402 protocol. It can:

🔌 Connect to multiple MCP servers at once (proxy)
💳 Handle 402 Payment Required automatically (x402)
📦 Provide programmatic APIs for clients and servers
🚀 Support both EVM and SVM networks for payments

Quick start

Install the CLI globally or use npx:

npm i -g mcpay
# or
npx mcpay connect -u "https://api.example.com/mcp" -a "<YOUR_API_KEY>"

Start a payment-aware stdio proxy to one or more MCP servers:

# Using an EVM private key (Payment transport)
mcpay connect -u "https://api.example.com/mcp" --evm 0x1234... --evm-network base-sepolia

# Using an SVM secret key (Payment transport)
mcpay connect -u "https://api.example.com/mcp" --svm <SECRET_KEY> --svm-network solana-devnet

# Using an API key only (HTTP transport)
mcpay connect -u "https://api.example.com/mcp" -a "$API_KEY"

Tip: You can pass multiple URLs: -u "https://api1/mcp,https://api2/mcp".

Installation

SDK (project dependency)

npm i mcpay
# or
pnpm i mcpay
# or
yarn add mcpay
# or
bun add mcpay

CLI

Commands

mcpay connect – start an MCP stdio proxy to remote servers with payment capabilities
mcpay version – show version information

Examples

# Basic (env vars)
export SERVER_URLS="https://api.example.com/mcp"
export EVM_PRIVATE_KEY="0x1234..."
mcpay connect -u "$SERVER_URLS"

# Multiple servers + API key header forwarded to remotes
mcpay connect -u "https://api1/mcp,https://api2/mcp" -a "$API_KEY"

# Using EVM wallet with specific network
mcpay connect -u "https://api.example.com/mcp" --evm 0x1234... --evm-network base

# Using SVM wallet
mcpay connect -u "https://api.example.com/mcp" --svm <SECRET_KEY> --svm-network solana

# Set maximum payment amount
mcpay connect -u "https://api.example.com/mcp" --evm 0x1234... --max-atomic 100000

Options

Option	Description	Default
`-u, --urls <urls>`	Comma-separated list of MCP server URLs	Required
`-a, --api-key <key>`	API key for authentication	`API_KEY` env
`--evm <privateKey>`	EVM private key (0x...)	`EVM_PRIVATE_KEY` env
`--svm <secretKey>`	SVM secret key (base58/hex)	`SVM_SECRET_KEY` env
`--evm-network <network>`	EVM network (base-sepolia, base, avalanche-fuji, avalanche, iotex, sei, sei-testnet)	`base-sepolia`
`--svm-network <network>`	SVM network (solana-devnet, solana)	`solana-devnet`
`--max-atomic <value>`	Max payment in atomic units	`X402_MAX_ATOMIC` env

Behavior:

If --evm or --svm is provided, the proxy uses Payment transport (x402) and can settle 402 challenges automatically.
If only --api-key is provided, the proxy uses standard HTTP transport and forwards the bearer token.
API keys can only be used with MCPay proxy URLs (mcpay.tech/v1/mcp/*).

Financial Server Integration Guide

MCP Client Integration

Connect to AI assistants like Claude, Cursor, and Windsurf.

One-Click Install for Cursor

If available on the website, use the "Install in Cursor" action to auto-generate an API key and configure your Cursor MCP settings.

Manual Configuration with API Key (Recommended)

Create an API key in your account settings and add this to your MCP client config (e.g., claude_desktop_config.json). Replace mcpay_YOUR_API_KEY_HERE with your real key.

{
  "mcpServers": {
    "Financial Server": {
      "command": "npx",
      "args": [
        "mcpay",
        "connect",
        "--urls",
        "https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0",
        "--api-key",
        "mcpay_YOUR_API_KEY_HERE"
      ]
    }
  }
}

Manual Configuration with EVM Private Key (Alternative)

Use a wallet private key instead of an API key. Replace with your own private key (handle securely).

{
  "mcpServers": {
    "Financial Server": {
      "command": "npx",
      "args": [
        "mcpay",
        "connect",
        "--urls",
        "https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0",
        "--evm",
        "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef",
        "--evm-network",
        "base-sepolia"
      ]
    }
  }
}

Manual Configuration with SVM Secret Key (Alternative)

Use a Solana secret key for SVM networks.

{
  "mcpServers": {
    "Financial Server": {
      "command": "npx",
      "args": [
        "mcpay",
        "connect",
        "--urls",
        "https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0",
        "--svm",
        "YOUR_SECRET_KEY",
        "--svm-network",
        "solana-devnet"
      ]
    }
  }
}

MCPay CLI (Direct Connection)

# Using API Key (recommended)
npx mcpay connect --urls https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0 --api-key mcpay_YOUR_API_KEY_HERE

# Using EVM Private Key (alternative)
npx mcpay connect --urls https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0 --evm 0xYOUR_PRIVATE_KEY --evm-network base-sepolia

# Using SVM Secret Key (alternative)
npx mcpay connect --urls https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0 --svm YOUR_SECRET_KEY --svm-network solana-devnet

Direct API Integration (JavaScript/TypeScript SDK)

import { Client } from '@modelcontextprotocol/sdk/client/index.js'
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js'
import { withX402Client } from 'mcpay/client'
import { createSigner } from 'x402/types'

// Initialize signer from private key
const evmSigner = await createSigner('base-sepolia', '0x1234567890abcdef...')
const url = new URL('https://mcpay.tech/v1/mcp/d67aaf0d-fcc8-4136-948d-c470abe41ac0')

// Create transport
const transport = new StreamableHTTPClientTransport(url)

// Initialize MCP client
const client = new Client(
  { name: 'my-mcp-client', version: '1.0.0' },
  { capabilities: {} }
)

await client.connect(transport)

// Wrap client with X402 payment capabilities
const paymentClient = withX402Client(client, {
  wallet: { evm: evmSigner },
  maxPaymentValue: BigInt(0.1 * 10 ** 6), // 0.1 USDC max payment
})

// Use tools with automatic payment handling
const tools = await paymentClient.listTools()
console.log('Available tools:', tools)

SDK usage

Programmatic stdio proxy

import { startStdioServer, createServerConnections, ServerType } from 'mcpay';
import { createSigner } from 'x402/types';

// Create signer for EVM network
const evmSigner = await createSigner('base-sepolia', '0x123...');
const serverConnections = createServerConnections(
  ['https://api.example.com/mcp'],
  ServerType.HTTPStream
);

const x402Config = {
  wallet: { evm: evmSigner },
  maxPaymentValue: BigInt(0.1 * 10 ** 6) // 0.10 USDC
};

await startStdioServer({ 
  serverConnections, 
  x402ClientConfig: x402Config 
});

Client: X402 Payment Wrapper

import { withX402Client } from 'mcpay/client';
import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
import { createSigner } from 'x402/types';

// Create signer
const evmSigner = await createSigner('base-sepolia', '0x123...');

// Initialize MCP client
const client = new Client(
  { name: 'my-app', version: '1.0.0' }, 
  { capabilities: {} }
);

const transport = new StreamableHTTPClientTransport(new URL('https://api.example.com/mcp'));
await client.connect(transport);

// Wrap with payment capabilities
const paymentClient = withX402Client(client, {
  wallet: { evm: evmSigner },
  maxPaymentValue: BigInt(0.1 * 10 ** 6) // 0.10 USDC
});

Protecting your MCP server with payments

Use createMcpPaidHandler to require a valid X-PAYMENT header (validated via x402) before your tools run. Works in serverless/edge-compatible runtimes.

import { createMcpPaidHandler } from 'mcpay/handler';
import { z } from 'zod';

const handler = createMcpPaidHandler(async (server) => {
  server.paidTool(
    'hello',
    'Say hello to someone',
    { price: 0.05, currency: 'USD' },
    { name: z.string().describe('Your name') },
    {},
    async ({ name }) => ({ 
      content: [{ type: 'text', text: `Hello, ${name}!` }] 
    })
  );
}, {
  recipient: {
    'base-sepolia': '0x1234567890abcdef1234567890abcdef12345678',
    'solana-devnet': 'So11111111111111111111111111111111111111112'
  },
  facilitator: {
    url: "FACILITATOR_URL"
  }
});

// Next.js (route handlers)
export { handler as GET, handler as POST, handler as DELETE };

Notes:

server.paidTool accepts a price object { price, currency } and recipient addresses for different networks.
When no valid payment is provided, the handler returns structured payment requirements that clients (like withX402Client) can satisfy.
The facilitator configuration connects to MCPay services for payment verification and settlement.

Environment variables

CLI:

EVM_PRIVATE_KEY: Hex private key for EVM x402 signing
SVM_SECRET_KEY: Secret key for SVM x402 signing
SERVER_URLS: Comma-separated MCP endpoints
API_KEY: Optional, forwarded as Authorization: Bearer <API_KEY> to remotes
X402_MAX_ATOMIC: Maximum payment amount in atomic units
EVM_NETWORK: EVM network (base-sepolia, base, avalanche-fuji, avalanche, iotex, sei, sei-testnet)
SVM_NETWORK: SVM network (solana-devnet, solana)

Server (payment auth):

MCPAY_API_URL (default https://mcpay.fun)
MCPAY_API_KEY

Transports

HTTPStream – standard streaming HTTP transport
withX402Client – wraps HTTP transport with automatic 402 Payment Required handling using x402 and your wallet

Payment protocol (x402)

On a 402 Payment Required response, MCPay will:

Parse the server-provided requirements
Create and sign an authorization with your wallet (EVM or SVM)
Retry the original request with X-PAYMENT header

Supported networks:

EVM: Base Sepolia, Base, Avalanche Fuji, Avalanche, IoTeX, Sei, Sei Testnet
SVM: Solana Devnet, Solana

Default USDC addresses are built-in per chain.

Troubleshooting

"Payment amount exceeds maximum allowed": increase maxPaymentValue in your x402ClientConfig.
Wrong chain/network: ensure your wallet/client network matches the server requirement.
Invalid private key: ensure EVM keys are 0x-prefixed 64-hex characters.
API key errors: ensure API keys are only used with MCPay proxy URLs (mcpay.tech/v1/mcp/*).

Development

pnpm i
pnpm run build
# Dev watch
pnpm run dev

Dependencies

@modelcontextprotocol/sdk - MCP protocol implementation
x402 - Payment protocol implementation
x402-fetch - Fetch integration for x402
viem - EVM blockchain interactions
commander - CLI framework
zod - Schema validation
mcp-handler - MCP server handler utilities

Security

Never commit private keys. Prefer environment variables and scoped, low-value keys for development.
Use the maxPaymentValue guard in clients and per-tool pricing in servers.

License

MIT

Contributing

Issues and PRs are welcome.

Support

Please open an issue in the repository.

Provide feedback

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MCPay SDK & CLI

Quick start

Installation

SDK (project dependency)

CLI

Commands

Examples

Options

Financial Server Integration Guide

MCP Client Integration

One-Click Install for Cursor

Manual Configuration with API Key (Recommended)

Manual Configuration with EVM Private Key (Alternative)

Manual Configuration with SVM Secret Key (Alternative)

MCPay CLI (Direct Connection)

Direct API Integration (JavaScript/TypeScript SDK)

SDK usage

Programmatic stdio proxy

Client: X402 Payment Wrapper

Protecting your MCP server with payments

Environment variables

Transports

Payment protocol (x402)

Troubleshooting

Development

Dependencies

Security

License

Contributing

Support

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README.md

Latest commit

History

README.md

File metadata and controls

MCPay SDK & CLI

Quick start

Installation

SDK (project dependency)

CLI

Commands

Examples

Options

Financial Server Integration Guide

MCP Client Integration

One-Click Install for Cursor

Manual Configuration with API Key (Recommended)

Manual Configuration with EVM Private Key (Alternative)

Manual Configuration with SVM Secret Key (Alternative)

MCPay CLI (Direct Connection)

Direct API Integration (JavaScript/TypeScript SDK)

SDK usage

Programmatic stdio proxy

Client: X402 Payment Wrapper

Protecting your MCP server with payments

Environment variables

Transports

Payment protocol (x402)

Troubleshooting

Development

Dependencies

Security

License

Contributing

Support