monospay-mcp

Pay per MCP tool call in USDC. Your agent gets a wallet, your paid tools get on-chain settlement on Base. No admin keys, no proxy, no custodian.

Quickstart (4 lines)

1. Get an API key at monospay.com/dashboard → Agents → API keys.
2. Paste this into your MCP config (Claude Desktop / Cursor / Windsurf):

   {"mcpServers":{"monospay":{"command":"npx","args":["-y","monospay-mcp"],"env":{"MONO_API_KEY":"mono_live_..."}}}}

3. Restart the client.
4. Ask: "Check my monospay balance".

To send payments, also set MONO_SESSION_TOKEN (issued in the same dashboard). Session tokens are short-lived bearers — revocable, never hold a private key.

What it does

Exposes monospay's payment primitives as MCP tools so any MCP-aware agent (Claude Desktop, Claude Code, Cursor, Windsurf) can:

• check balance, view transactions, set spending limits — with API key only
• transfer USDC on Base mainnet — with a session token

That same flow lets paid MCP servers charge agents per tool call: the server returns a quote, the agent pays via monospay, the server verifies the on-chain receipt before returning the tool result.

Configuration

Claude Desktop — claude_desktop_config.json:

{
  "mcpServers": {
    "monospay": {
      "command": "npx",
      "args": ["-y", "monospay-mcp"],
      "env": {
        "MONO_API_KEY": "mono_live_...",
        "MONO_SESSION_TOKEN": "mono_sess_..."
      }
    }
  }
}

Claude Code:

claude mcp add monospay \
  -e MONO_API_KEY=mono_live_... \
  -e MONO_SESSION_TOKEN=mono_sess_... \
  -- npx -y monospay-mcp

Cursor / Windsurf — same JSON block in the editor's MCP settings.

Capability matrix

| | API key only | + Session token | + Private key (deprecated) | |---|---|---|---| | Check balance | yes | yes | yes | | View transactions | yes | yes | yes | | Set spending limits | yes | yes | yes | | Pay paid tool calls | no | yes (revocable) | yes (legacy) |

Session tokens are the recommended path. Private keys keep working with a deprecation notice on each launch.

"env": {
  "MONO_API_KEY": "mono_live_...",
  "MONO_PRIVATE_KEY": "0x..."
}

How it runs

This package is a thin Node launcher. On first run it bootstraps a Python virtualenv at <tmp>/monospay-mcp-venv and installs monospay[mcp] from PyPI. The MCP server itself is Python — the signing path uses eth-account for EIP-191, which has no Node equivalent of comparable correctness. Subsequent runs reuse the venv.

[monospay-mcp] First run — bootstrapping a Python virtualenv.
[monospay-mcp] [1/3] Creating virtualenv...
[monospay-mcp] [2/3] Upgrading pip (quiet)...
[monospay-mcp] [3/3] Installing monospay[mcp] from PyPI...
[monospay-mcp] Ready. Starting MCP server.

Requirements: Python 3.10+ on PATH (python3 or python), Node 18+, outbound HTTPS to pypi.org on first run.

Building a paid MCP server?

The receive side runs against the monospay HTTP API. Your tool issues a quote, waits for on-chain settlement, then returns the result. Implementation reference: monospay Python SDK. Open an issue or email [email protected] for early integration help.

Links

• monospay.com — Dashboard
• GitHub — Source
• PyPI — Python SDK