Turn any AI API into a
paid API in minutes.
No monthly fee. Pay 3% only when your AI API earns.
Start free — your first 3,000 calls, with gateway, Pay Token, spend limits, and metering all included.
Currently shipping: SDK (lc.charge, lc.protect) — MIT, on npm today.
Q3 2026: hosted gateway, Pay Token issuance, margin dashboard. Design partners get early access.
Used by xstocks-mcp · gmx-mcp · alpaca-guard-mcp · tokenized-stock-mcp · agent-payment-mcp
import { createLemonCakeSDK } from "@lemon-cake/mcp-sdk";
const lc = createLemonCakeSDK(); // demo mode without env vars
// HTTP route — one line.
app.use(lc.protect("/api/search", { cost: 0.02 }));
// Or an MCP tool — same idea.
server.tool("search", lc.charge({ price: 0.02 }), handler);Drop-in MCP middleware. Works with any MCP SDK. Free for your first 3,000 calls.
How it works
Four boxes between you
and per-call revenue.
You change one URL. We do gateway routing, Pay Token verification, rate limiting, usage metering, and settle the 97% to your wallet.
Why developers use LemonCake
Built for the things
payment infra makes annoying.
Six things you stop worrying about after wiring up LemonCake.
Usage-based billing
Charge per tool call, per token, per outcome. Sub-cent micro-payments work natively — no minimum transaction size, no Stripe-style $0.30 floor.
AI agent payments
Agents pay your endpoint directly with one-time spend caps. No human in the loop, no API-key sharing, no "reset my credentials" support tickets.
No API-key management
Stop issuing, rotating, and revoking keys. Buyers authenticate once at install time; you never touch their secrets.
Global by default
Works in countries where Stripe Connect doesn't. Japan, Indonesia, Argentina — supported on day one.
Embedded wallet
Your buyers don't need a crypto wallet. We embed one at signup; they sign in with email and forget the underlying mechanics.
MCP-native
Drop-in middleware for any MCP server. Auto-listing on Bazaar + Glama + Smithery + mcp.so + Claude Code Plugins Directory.
The billing stack today
Stripe is for humans. Orb & Metronome are for SaaS.
LemonCake is for AI.
Existing billing infra assumes a human swipes a card and an org renews a seat. AI APIs charge sub-cent per call to a non-human caller. Different shape — different stack.
| Stripe | Orb / Metronome | LemonCake | |
|---|---|---|---|
| Meter + invoice + pay in one SDK | Pay only | Meter + invoice (pay via Stripe) | Yes |
| AI agent as buyer | Card-only | Org-billed only | Native |
| Sub-cent per call | $0.30 effective floor | Allowed, but Stripe-billed | $0.005 |
| MCP / agent middleware | — | — | Drop-in |
| No API-key management | Keys still required | Keys still required | Embedded auth |
| Free tier | Stripe rates apply | Enterprise tiers | 1k tx / mo, gas covered |
| Open-source SDK | Closed | Closed | MIT |
| Setup time | Connect onboarding | Implementation engineer | One env var |
We don't replace Stripe for human checkout. We're the stack you want when the buyer is an AI agent.
Not just billing — abuse prevention
We block runaway agents.
Before they cost you anything.
Pay Token spend caps + rate limits are checked at the gateway. A misbehaving agent in an infinite loop hits the wall instantly — your API never sees the request, your AWS bill never moves. The blocked-request feed in your dashboard shows you what we caught.
Sample data — live feed lands Q3 2026.
Coming Q3 2026 · Early access
Margin dashboard.
AI cost vs. revenue per agent, per endpoint, per token. Catch margin leaks before they compound. The metric Stripe / Orb / Metronome don't natively show — because their buyers don't have $0.50 of OpenAI cost behind every $0.05 of revenue. Yours do.
Open core, like Supabase & Clerk
Fork the SDK.
Let us host the boring stuff.
Pure-OSS billing infra dies the moment funding does. Pure-SaaS billing infra is lock-in by design. Open core is the only honest middle: MIT-licensed SDK + hosted execution. If we vanish, your integration keeps working.
What you can fork
- ● @lemon-cake/mcp-sdk
- ● @lemon-cake/x402-server
- ● agent-payment-mcp
- ● examples/* (starter templates)
- ● MCP adapters (Claude / Cursor / LangChain)
- ● All docs and migration guides
What we run as a service
- ● Billing engine (settlement, ledger)
- ● Revenue routing & payout logic
- ● Dashboard (analytics, payouts, abuse)
- ● Compliance (tax, invoicing, reporting)
- ● Fraud / abuse detection
- ● Hosted gateway & uptime SLA
MIT · Supabase / Clerk / Resend pattern · 5 production MCPs published
Safety rails
Kill switch
One-click revoke on the dashboard. Subsequent charges return 422 atomically.
Tiered limits (KYA)
$10/day default → $1k/day with Know-Your-Agent → $50k/day with full KYC.
Sandbox mode
Issue test tokens that match production behavior but never move real USDC.
Launch Plan · Private Beta
Turn your AI API into
a paid API today.
No monthly fee. Pay 3% only when your API earns. Start free — your first 3,000 calls, with gateway, Pay Token, spend limits, and metering all included.
No credit card. Manual onboarding (~24h) during Private Beta.