Using Stripe's Machine Payments Protocol as an MCP Client

Stripe's Machine Payments Protocol (MPP) enables AI agents to autonomously pay for tool usage on monetized MCP servers. Instead of a human manually authorizing each API call with a credit card, your agent holds an isolated "Machine Wallet" payment budget and settles micro-payments securely per tool call.

Prerequisites

• ▸A Stripe account with developer access.
• ▸Funds added to your Stripe account balance to fund the Machine Wallet.
• ▸An MCP client framework that supports custom server adapters.

Step 1: Create a Machine Wallet

A machine wallet is a new Stripe primitive that represents an AI agent's payment identity and strict spending budget.

curl https://api.stripe.com/v1/machine_wallets \
  -u sk_live_your_secret_key: \
  -d "display_name=My Code Assistant Agent" \
  -d "budget[amount]=10000" \
  -d "budget[currency]=usd" \
  -d "budget[period]=monthly"

Step 2: Install the MPP MCP Client Adapter

npm install @stripe/mcp-mpp-adapter

Step 3: Configuration Setup

You must map the specific paid server (e.g., a proprietary legal database MCP server) through the Stripe MPP adapter. Add the MPP credentials to your Claude Desktop or custom agent config:

{
  "mcpServers": {
    "premium-legal-database": {
      "command": "npx",
      "args": ["-y", "@stripe/mcp-mpp-adapter"],
      "env": {
        "UPSTREAM_MCP_SERVER": "https://api.legal-mcp-server.com/mcp",
        "STRIPE_MACHINE_WALLET_ID": "mw_live_abc123",
        "STRIPE_MACHINE_WALLET_SECRET": "mws_live_xyz789",
        "MPP_MAX_PER_TOOL_CALL_USD": "0.50",
        "MPP_REQUIRE_CONFIRMATION_ABOVE_USD": "1.00"
      }
    }
  }
}

Step 4: Spending Controls & Best Practices

You can and should fine-tune your AI's spending behavior using environment variables. AI agents can get stuck in loops; without limits, a stuck agent could drain your wallet in minutes.

Troubleshooting

• ▸402 Payment Required: The upstream MCP server rejected the tool call because the MPP payment header was missing or invalid. Verify your STRIPE_MACHINE_WALLET_SECRET.
• ▸Insufficient Funds: The agent has exhausted the budget allocated to its STRIPE_MACHINE_WALLET_ID. You must use the Stripe API or Dashboard to top up the machine wallet.
• ▸Agent Hallucinating Tool Costs: Sometimes agents try to negotiate pricing with the MCP server via JSON-RPC. Ensure your agent system prompt explicitly states that it does not negotiate prices; the MPP adapter handles the transaction layer.

Using with OpenAI Codex

You can use this MCP server with the OpenAI Codex CLI by adding it to your configuration:

codex mcp add --name stripe --command "npx -y @modelcontextprotocol/server-stripe" --env STRIPE_SECRET_KEY=sk_your_key

Note: This configures the Stripe MCP server, which your Codex agent can then use as a client.

For a full list of recommended servers, see Best MCP Servers for OpenAI Codex.