Pay MCP Server

@pay-skill/mcp

MCP server for Pay -- the complete x402 payment stack for AI agents. USDC on Base.

Gives any MCP-compatible client (Claude Desktop, Cursor, VS Code, custom frameworks) the full power of Pay: direct payments, tabs, x402 paywalls, service discovery, and wallet management. No CLI binary needed.

Setup

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "pay": {
      "command": "npx",
      "args": ["-y", "@pay-skill/mcp"]
    }
  }
}

VS Code / Cursor

Add to .vscode/mcp.json:

{
  "servers": {
    "pay": {
      "command": "npx",
      "args": ["-y", "@pay-skill/mcp"]
    }
  }
}

Claude Code

claude mcp add pay -- npx -y @pay-skill/mcp

That's it. On first run, the server generates a wallet and stores it in the OS keychain (Windows Hello, macOS Keychain, Linux Secret Service). Subsequent runs load it automatically.

Configuration

| Env Var | Required | Default | Description | |---------|----------|---------|-------------| | PAYSKILL_SIGNER_KEY | No | — | Optional override. Raw hex key or .enc keystore password. Not needed for normal use. | | PAY_NETWORK | No | mainnet | mainnet (Base) or testnet (Base Sepolia) |

Key Resolution (checked in order)

1. OS keychain (default) — Loads from the OS credential store via keytar. On first run, a new keypair is generated and stored automatically.
2. Encrypted keystore — If ~/.pay/keys/default.enc exists, PAYSKILL_SIGNER_KEY is used as the decryption password.
3. Raw hex key — If PAYSKILL_SIGNER_KEY is a 64-char hex string, it's used directly. For dev/testing or importing an existing wallet.
4. Auto-generate — If none of the above, generates a new keypair and stores it in the OS keychain.

Diagnostic Check

Verify everything is configured correctly:

npx @pay-skill/mcp --check

Output: ``` pay-mcp diagnostic check network: Base (chain 8453) api: https://pay-skill.com/api/v1 wallet: 0x1234... key: keychain server: OK (router: 0xABCD...) auth: OK (balance: $50.00)

All checks passed. MCP server is ready. ```

Tools (15)

Payments

| Tool | Description | |------|-------------| | pay_send | Direct USDC payment ($1 min). Confirmation thresholds: <$10 auto, $10-100 plan, >$100 explicit. | | pay_request | HTTP request with x402 auto-payment. Handles 402 detection, direct/tab settlement, price skepticism. |

Tabs (metered accounts)

| Tool | Description | |------|-------------| | pay_tab_open | Open pre-funded tab ($5 min, $50 recommended). Provider charges per-call. | | pay_tab_close | Close tab. Returns distribution breakdown (provider 99%, fee 1%, agent remainder). | | pay_tab_charge | Charge against open tab (provider only). | | pay_tab_topup | Add funds to open tab (agent only). | | pay_tab_list | List tabs with idle/low-balance flags. |

Wallet

| Tool | Description | |------|-------------| | pay_status | Balance, locked/available funds, actionable suggestions. | | pay_fund | Generate 1-hour funding link (Coinbase Onramp or direct USDC). | | pay_withdraw | Generate 1-hour withdrawal link. | | pay_mint | Mint testnet USDC (Base Sepolia only). |

Discovery & Webhooks

| Tool | Description | |------|-------------| | pay_discover | Search paid API services by keyword/category. | | pay_webhook_register | Register webhook for payment events (HMAC-signed). | | pay_webhook_list | List registered webhooks. | | pay_webhook_delete | Delete a webhook. |

Resources (5)

| URI | Description | |-----|-------------| | pay://wallet/status | Balance, tabs, locked/available | | pay://wallet/tabs | All open tabs | | pay://tab/{tab_id} | Single tab detail | | pay://wallet/address | Wallet address | | pay://network | Network config + contract addresses |

Prompts (3)

| Prompt | Description | |--------|-------------| | pay-for-service | Guided: discover service, evaluate pricing, make request | | review-tabs | Review tabs, flag idle, suggest close/topup | | fund-wallet | Generate fund link, explain deposit process |

Development

git clone https://github.com/pay-skill/pay-mcp.git
cd pay-mcp
npm install
npm run build
npm test                    # unit tests (mocked)
npm run test:acceptance     # testnet (requires PAYSKILL_TESTNET_KEY)

License

MIT

Part of Pay

Pay is the complete x402 payment stack -- gateway, facilitator, SDKs, CLI, and MCP server -- that lets AI agents pay for APIs with USDC on Base.

• Documentation
• Architecture
• SDK -- Python + TypeScript
• CLI -- Command-line tool
• pay-gate -- x402 payment gateway
• Protocol -- Smart contracts