agent-payment-mcp 🍋

Stripe-style drop-in USDC billing for any HTTP API. Try in 5 seconds, zero signup.

⚡ Try in 5 seconds

Easiest — Glama Playground (no install)

👉 Hit "Try in Browser" at the top of this page. Demo Mode starts instantly, no env vars needed.

Claude Desktop / Cursor / Cline

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (or your Cursor / Cline MCP config):

{
  "mcpServers": {
    "lemon": {
      "command": "npx",
      "args": ["-y", "agent-payment-mcp"]
    }
  }
}

Restart, then ask:

"use lemon to translate 'Hello, agent payments' to Japanese"

or

"use lemon to get current weather in Akihabara"

Zero env vars. Zero signup. Zero credit card. Demo Mode activates automatically.

🎁 8 free demo tools (real APIs, no auth)

All powered by real free upstreams. Useful enough that many users never need to upgrade.

Plus check_tax — live Japanese 適格請求書 (T+13) validation against 国税庁. No other LLM can do this without hallucinating.

Compose them: demo_geocode → demo_weather ("weather in Tokyo"), demo_translate → demo_dictionary, etc.

📊 vs Stripe (when you go live)

💳 Unlock paid services — when you need more

Need Serper (Google search) / Hunter.io (verified emails) / Tavily / Firecrawl / gBizINFO (JP corporate registry)? One 90-day signature unlocks all of them:

1. Open lemoncake.xyz/start/v2
2. Google sign-in (Privy embedded wallet — keys stay on your device)
3. Sign ONE ERC-2612 permit — $25/day cap, 90 days, gas-free
4. Copy the LEMON_CAKE_PERMIT blob
5. Add to your MCP config:

{
  "mcpServers": {
    "lemon": {
      "command": "npx",
      "args": ["-y", "agent-payment-mcp"],
      "env": { "LEMON_CAKE_PERMIT": "<paste the permit blob>" }
    }
  }
}

That's it. Every API call settles directly from your wallet to the provider on Base. LemonCake never touches your USDC.

🏪 Publish your own API (for sellers)

Want to monetize your MCP / HTTP API? Self-service registration at lemoncake.xyz/sellers:

• 1-minute signup (name / email / Base wallet address — no KYC)
• Get a serviceId instantly
• First 1,000 calls / month free (LemonCake absorbs)
• Above: $0.001/call (you set the price, 100% to you)
• USDC settles directly to your wallet on every call

Add billing in 3 lines:

import { x402Hono } from "@lemon-cake/x402-server";

app.use("/api/search", x402Hono({
  serviceId:       "your-providerV2-id",
  pricePerCallUsd: 0.001,
  facilitator:     "both",  // Coinbase Bazaar + LemonCake metering
}));

Hybrid facilitator: "both" mode → settle through Coinbase CDP for x402 Bazaar / AWS Bedrock AgentCore discoverability, while LemonCake records the call for freee/MF auto-journal + 適格請求書 + JPY off-ramp (Pro plan).

🌍 Compliance — registration-exempt in 7 jurisdictions

The 2026-05-21 ruling from Japan's FSA Fintech Support Desk (Q11) confirmed that a pure non-custodial SDK model does NOT require the "electronic payment means management" registration.

Same architecture is exempt under:

Full posture: lemoncake.xyz/security.

🔌 The LemonCake family

🛡 Security

• On-chain hard cap — the daily $25 limit is enforced by the USDC contract itself. The agent literally cannot exceed it.
• No private keys in the MCP server — the permit blob is a scope-limited EIP-712 signature.
• Auto-revoke on expiry — permits self-destruct after 90 days.
• Idempotency keys required on paid calls (no double-charges on retries).
• Audited May 2026 by @kleosr. See security advisories.

Links