@paypertool/mcp

MCP server that lets AI agents discover and pay for PayPerTool tools per HTTP call in USDC on Base via the x402 protocol. No signup, no API keys, no subscriptions — your agent holds a hot wallet and pays $0.0005-$0.02 per call.

Hot wallet warning. This package needs a private key on disk to sign EIP-3009 USDC authorizations. Treat the wallet as a small, refillable spending account. Never use a key that holds significant funds. For production agents, prefer a managed signer (CDP Wallet, Privy, Turnkey) over plaintext config.

Install (Claude Desktop)

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "paypertool": {
      "command": "npx",
      "args": ["-y", "@paypertool/mcp"],
      "env": {
        "PAYPERTOOL_PRIVATE_KEY": "0x...",
        "PAYPERTOOL_BASE_URL": "https://web-production-a4921.up.railway.app",
        "PAYPERTOOL_NETWORK": "base"
      }
    }
  }
}

Restart Claude. The full PayPerTool catalog (scrape_url, search_web, screenshot, extract_data, youtube_transcript, og_metadata, ens_resolve, gas_price, token_info, rugcheck, agent_memory_set, agent_memory_get) appears as native tools.

Works with any MCP-compatible client (Cursor, Cline, Continue, custom agents).

Funding the wallet

Send a small amount of native USDC on Base to the wallet address that corresponds to your PAYPERTOOL_PRIVATE_KEY. No ETH needed — the x402 facilitator pays gas. EIP-3009 is gasless for the buyer.

• Base mainnet USDC contract: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
• Topping up $1-$5 covers hundreds of calls.

For testing without real money, set PAYPERTOOL_NETWORK=base-sepolia and use the Base Sepolia faucet (faucet.circle.com).

Environment variables

| var | required | default | | ------------------------- | -------- | ---------------------------------------------------- | | PAYPERTOOL_PRIVATE_KEY | yes | — | | PAYPERTOOL_BASE_URL | no | https://web-production-a4921.up.railway.app | | PAYPERTOOL_SERVER_URL | no | (alias for PAYPERTOOL_BASE_URL) | | PAYPERTOOL_NETWORK | no | base (use base-sepolia for testing) |

How it works (the HTTP exchange)

1. Agent: POST /api/tools/scrape  { "url": "https://example.com" }
2. Server: 402 Payment Required + payment requirements (USDC amount, payTo, network)
3. Agent: signs EIP-3009 transferWithAuthorization with its hot wallet
4. Agent: POST /api/tools/scrape with X-PAYMENT header
5. Facilitator: verifies + settles on Base (gasless for buyer)
6. Server: 200 OK + result + X-PAYMENT-RESPONSE (settlement tx hash)

The MCP server handles steps 3 + 4 + 6 transparently. The agent just calls the tool.

Links

• Website: https://web-production-a4921.up.railway.app
• Source: https://github.com/ttcarter38-max/paypertool
• x402 protocol: https://x402.org
• MCP spec: https://modelcontextprotocol.io

License

MIT