AI42 MCP Server

X402 Payment MCP Server for Claude Desktop

Quick Start • Features • Installation • Usage

Overview

AI42 MCP Server enables Claude Desktop to automatically handle web requests with X402 payments. Fetch data from any URL and seamlessly process cryptocurrency payments when required (402 status). Includes payment tracking, balance checking, and spending limits.

Features

• Automatic Payment Handling: Transparent X402 payment processing on 402 responses

• GET & POST Support: Full HTTP method support for API interactions

• Payment Management: Track history, check balance, set spending limits

• Solana Integration: Built on Solana devnet/mainnet

• Type-safe: Full TypeScript support

• Zero Configuration: Works out of the box with Claude Desktop

Available Tools

Installation

Prerequisites

• Node.js 18+

• Solana wallet private key (base58 format)

• Claude Desktop

Quick Install

No manual installation needed! Just configure Claude Desktop:

Add to

Windows:

{
  "mcpServers": {
    "x402-payment": {
      "command": "npx",
      "args": ["-y", "@ai42/mcp"],
      "env": {
        "SOLANA_PRIVATE_KEY": "your_base58_private_key_here"
      }
    }
  }
}

macOS:

{
  "mcpServers": {
    "x402-payment": {
      "command": "npx",
      "args": ["-y", "@ai42/mcp"],
      "env": {
        "SOLANA_PRIVATE_KEY": "your_base58_private_key_here"
      }
    }
  }
}

Linux:

{
  "mcpServers": {
    "x402-payment": {
      "command": "npx",
      "args": ["-y", "@ai42/mcp"],
      "env": {
        "SOLANA_PRIVATE_KEY": "your_base58_private_key_here"
      }
    }
  }
}

Config File Locations

After adding config: Restart Claude Desktop!

Quick Start

Getting Your Private Key

Generate Solana Keypair:

solana-keygen new --outfile ~/.config/solana/id.json
solana-keygen pubkey ~/.config/solana/id.json

Export Private Key (base58 format):

cat ~/.config/solana/id.json
# Copy the array, then convert to base58

⚠️ Never commit private keys to version control!

First Request

Once configured and Claude Desktop is restarted, simply ask:

You: Check my wallet balance

Claude: [Uses get-balance tool] Your balance is 2.5 SOL on devnet

Usage

Example Conversations

Fetch Data from URL

You: Get data from https://api.example.com/endpoint

Claude: [Uses fetch-with-payment] Here's the data from the API...

Fetch with Payment

You: Fetch https://paid-service.com/premium-data

Claude: [Uses fetch-with-payment] Payment of 0.05 SOL made successfully. 
Here's the premium data...

POST Request

You: POST this data to https://api.example.com: {"message": "hello"}

Claude: [Uses fetch-with-payment] Successfully posted. Response: {...}

Check Balance

You: What's my SOL balance?

Claude: [Uses get-balance] Your current balance:
- Balance: 2.5 SOL
- Network: devnet
- Address: 7xK...abc

Set Payment Limit

You: Set payment limit to 0.1 SOL

Claude: [Uses set-payment-limit] Payment limit set to 0.1 SOL. 
Any request exceeding this amount will be rejected.

View Payment History

You: Show my payment history

Claude: [Uses get-payment-history] 
Total payments: 3
Total spent: 0.15 SOL

Recent payments:
1. 0.05 SOL to xyz...abc at 2025-11-12T10:30:00Z
2. 0.08 SOL to def...123 at 2025-11-12T11:45:00Z
3. 0.02 SOL to ghi...789 at 2025-11-12T12:15:00Z

Tool Reference

1. fetch-with-payment

Fetch data from any URL with automatic payment handling.

Parameters:

• url (string, required): URL to fetch

• method (string, optional): HTTP method - "GET" or "POST" (default: "GET")

• body (string, optional): JSON string for POST requests

Returns:

{
  success: boolean;
  data: any;
  payment_made: boolean;
  payment_amount: number; // in SOL
}

Example:

Get data from https://api.weather.com/current

2. get-balance

Check current SOL balance in your wallet.

Parameters: None

Returns:

{
  balance: number;      // SOL amount
  unit: "SOL";
  network: string;      // "devnet" or "mainnet"
  address: string;      // Public key
}

Example:

Check my wallet balance

3. get-payment-history

View all payments made during the current session.

Parameters:

• limit (number, optional): Maximum records to return (default: all)

Returns:

{
  total_payments: number;
  total_spent: number;     // Total SOL spent
  records: Array<{
    url: string;
    amount: number;        // in SOL
    recipient: string;
    timestamp: string;
    signature: string;
  }>;
}

Example:

Show last 5 payments

4. set-payment-limit

Set maximum spending limit per request. Set to 0 to remove limit.

Parameters:

• limit (number, required): Maximum SOL amount (0 to remove)

Returns:

{
  message: string;
  current_limit: number | null;
}

Example:

Don't let me spend more than 0.05 SOL per request

How It Works

The X402 Payment Flow

1. Request: Claude makes a request to a URL

2. 402 Response: If the endpoint requires payment, it returns HTTP 402

3. Automatic Payment: The MCP server automatically processes the payment using your Solana wallet

4. Retry: The request is retried with payment proof

5. Success: Data is returned to Claude

Payment Tracking

• All payments are logged in-memory during the session

• Track amounts, recipients, timestamps, and transaction signatures

• View history anytime with get-payment-history

Spending Limits

• Set a maximum amount per request to prevent overspending

• Requests exceeding the limit are automatically rejected

• Remove limits by setting to 0

Advanced Usage

Testing with MCP Inspector

For development and debugging:

# Install globally or use npx
npx @modelcontextprotocol/inspector npx @ai42/mcp

This opens a web UI where you can:

• See all registered tools

• Test tool calls with custom inputs

• View request/response JSON

• Debug payment flows

Environment Variables

If running locally (not via npx in Claude config):

# .env file
SOLANA_PRIVATE_KEY=your_base58_private_key_here

Network Configuration

Currently supports:

• Solana Devnet (default): For testing with test SOL

• Solana Mainnet: For production (update in source)

Security Best Practices

Private Key Safety

✅ DO:

• Store private keys in environment variables

• Use separate wallets for testing (devnet) and production (mainnet)

• Set reasonable payment limits

• Regularly check payment history

❌ DON'T:

• Commit private keys to git

• Share private keys in chat or screenshots

• Use production wallets without payment limits

• Ignore payment history

Payment Limits

Recommended limits based on usage:

Troubleshooting

"Bad secret key size" error

Your private key format is incorrect. Ensure it's in base58 format:

# Convert from JSON array to base58
node -e "console.log(require('bs58').encode(Buffer.from([your,array,here])))"

"Module not found" error

Clear npx cache and reinstall:

npx clear-npx-cache
# Restart Claude Desktop

"Payment failed" error

Check:

1. Wallet has sufficient balance (get-balance)

2. Network connectivity to Solana RPC

3. Private key is valid

4. Payment limit not exceeded

Tool not appearing in Claude

1. Verify config file location and syntax

2. Restart Claude Desktop completely

3. Check Claude Desktop logs for errors

4. Test with MCP Inspector

Development

Local Development

# Clone repository
git clone https://github.com/Kishore-MK/ai42-mcp
cd ai42-mcp

# Install dependencies
npm install

# Create .env file
echo "SOLANA_PRIVATE_KEY=your_key" > .env

# Build
npm run build

# Test locally
node dist/index.js

Project Structure

ai42-mcp/
├── src/
│   ├── index.ts          # Main MCP server
|   ├── payment.ts        # Payment client wrapper
│   └── types.ts          # Types file
├── dist/                 # Compiled JavaScript
├── package.json
├── tsconfig.json
└── README.md

Contributing

Contributions welcome! Please feel free to submit a Pull Request.

1. Fork the repository

2. Create your feature branch (git checkout -b feature/amazing-feature)

3. Commit your changes (git commit -m 'Feat: Add amazing feature')

4. Push to the branch (git push origin feature/amazing-feature)

5. Open a Pull Request

Links

• 📦 NPM Package: @ai42/mcp

• 💻 GitHub Repository: ai42-mcp

• 📖 X402 Protocol: x402.org

• 🔧 MCP SDK: @modelcontextprotocol/sdk

License

MIT License - see LICENSE file for details

Acknowledgments

Built with:

• X402 Protocol - HTTP 402 payment standard

• x402-fetch - Payment wrapper for Node.js

• Model Context Protocol - MCP SDK

• @solana/web3.js - Solana blockchain interaction

Made with ❤️ by keyaru

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