paypay-mcp
Model Context Protocol server for the PayPay Open Payment API.
Works with Claude Desktop, Claude Code, Cursor, Windsurf, Zed, ChatGPT Apps SDK, and any other MCP-compatible client. Tool descriptions are provided in English and Japanese.
Status
v0.2.x — production-capable, not yet battle-tested at scale.
The server runs cleanly against PayPay's production Open Payment API once PAYPAY_ENV=production is set with approved merchant credentials. It has not yet processed meaningful real-world volume. If you are routing real payments through it, pin the version and review the source first.
| Tool | Description |
|---|
create_qr_code | Create a dynamic PayPay QR code. Returns the payment URL, deeplink, and a rendered PNG. |
get_payment_details | Fetch the current status of a payment. |
wait_for_payment | Poll until a payment reaches a terminal state. |
delete_qr_code | Invalidate a QR code before payment. |
refund_payment | Full or partial refund. Disabled unless PAYPAY_ENABLE_REFUNDS=true. |
cancel_payment | Cancel a payment when its state is unclear (timeout or error). Disabled unless PAYPAY_ENABLE_CANCELS=true. |
Prompts
accept_single_payment, refund_last_payment, debug_stuck_payment.
Resources
| URI | Description |
|---|
paypay://docs/opa-reference | Endpoint map, auth scheme, and status vocabulary for the PayPay OPA API. |
paypay://docs/payment-states | Payment lifecycle and the cancel-vs-refund decision rule. |
paypay://config/current | Non-secret view of the active config (env, merchantId, baseUrl, transport). |
Install
One-click:
Or via npm:
npm install -g paypay-mcp
Configuration
Credentials come from the PayPay Developer Dashboard.
| Variable | Required | Description |
|---|
PAYPAY_API_KEY | yes | OPA API Key ID |
PAYPAY_API_SECRET | yes | OPA API Key Secret |
PAYPAY_MERCHANT_ID | yes | Merchant ID |
PAYPAY_ENV | no | sandbox (default) or production |
PAYPAY_ENABLE_REFUNDS | no | Set to true to expose refund_payment. Disabled by default. |
PAYPAY_ENABLE_CANCELS | no | Set to true to expose cancel_payment. Disabled by default. |
MCP_TRANSPORT | no | stdio (default) or http |
MCP_HTTP_PORT | no | Port when MCP_TRANSPORT=http. Default 3000. |
MCP_HTTP_HOST | no | Bind address. Default 127.0.0.1. Public binds require MCP_AUTH_TOKEN. |
MCP_AUTH_TOKEN | no | Bearer token required on inbound HTTP requests when set. Mandatory for non-loopback binds. |
MCP_HTTP_ALLOWED_ORIGINS | no | Comma-separated CORS allowlist. Default: none. |
Claude Desktop
Edit ~/Library/Application Support/Claude/claude_desktop_config.json:
{
"mcpServers": {
"paypay": {
"command": "npx",
"args": ["-y", "paypay-mcp"],
"env": {
"PAYPAY_API_KEY": "a_...",
"PAYPAY_API_SECRET": "...",
"PAYPAY_MERCHANT_ID": "...",
"PAYPAY_ENV": "sandbox"
}
}
}
}
Claude Code
claude mcp add paypay -e PAYPAY_API_KEY=... -e PAYPAY_API_SECRET=... -e PAYPAY_MERCHANT_ID=... -- npx -y paypay-mcp
Cursor
Add to ~/.cursor/mcp.json with the same shape as Claude Desktop.
Remote hosting
Run in HTTP mode. Public binds require MCP_AUTH_TOKEN; the server refuses to start otherwise.
MCP_TRANSPORT=http \
MCP_HTTP_HOST=0.0.0.0 \
MCP_AUTH_TOKEN="$(openssl rand -hex 32)" \
MCP_HTTP_ALLOWED_ORIGINS="https://claude.ai,https://your-app.example.com" \
PAYPAY_ENV=sandbox \
PAYPAY_API_KEY=... PAYPAY_API_SECRET=... PAYPAY_MERCHANT_ID=... \
npx paypay-mcp
Endpoint: POST http(s)://<host>:3000/mcp (Streamable HTTP transport). Clients send Authorization: Bearer <MCP_AUTH_TOKEN>. CORS is closed by default.
For local testing the auth token can be omitted; the server binds to 127.0.0.1 and only accepts loopback connections.
Environments
Sandbox is the default. Production requires PayPay merchant onboarding (business verification and a contract) and must be enabled by explicitly setting PAYPAY_ENV=production.
Constraints
- Amounts are integer JPY.
- A payment can be canceled until 00:14:59 JST the day after the payment attempt. After that, use a refund.
- A single order can receive multiple partial refunds, each with a unique
merchantRefundId, up to the merchant-configured cap.
- TLS 1.2+ required (Node 20+).
Development
git clone https://github.com/mrslbt/paypay-mcp.git
cd paypay-mcp
npm install
cp .env.example .env
npm run dev
npm test
npm run smoke
npm run build
Roadmap
v0.2: PreAuth + Capture, ContinuousPayments, DirectDebit, AccountLink QR, webhook signature verification, reconciliation tools.
v0.3: Native Payment (App Invoke + user JWT auth), Visa-partnership endpoints, OpenTelemetry tracing.
Safety
This server can move real money through the PayPay OPA API. Key safeguards:
- Refund and cancel tools are disabled by default.
refund_payment and cancel_payment are only registered when PAYPAY_ENABLE_REFUNDS=true or PAYPAY_ENABLE_CANCELS=true. Only enable them in trusted agent contexts where tool inputs cannot be influenced by untrusted content.
- Sandbox is the default. Production requires an explicit
PAYPAY_ENV=production, plus completed PayPay merchant onboarding. Always test against sandbox first.
- Unique merchantPaymentId and merchantRefundId per call. PayPay deduplicates by these IDs, so reusing one will either fail or target an older payment. Generate a fresh ID for each new payment or refund.
- Tools carry MCP safety annotations. Read-only tools (
get_payment_details, wait_for_payment) are flagged readOnlyHint; money-moving and destructive tools (refund_payment, cancel_payment, delete_qr_code) are flagged destructiveHint so compatible clients can warn you before the call. These are advisory hints — the real guard is the gating above.
Even with these gates on, review any money-moving request before approving the tool call. Treat tool inputs derived from model output as untrusted.
Disclaimer
This is an unofficial, community-built MCP server. Not affiliated with, endorsed by, or sponsored by PayPay Corporation. PayPay is a registered trademark of its respective owners. Use at your own risk. The author accepts no liability for funds lost through misuse, prompt injection, or bugs.
License
MIT