FAQ

General

What is MCPay?
MCPay is a payment layer for MCP and HTTP servers. It implements the x402 protocol, which lets any client (human app or AI agent) call a tool, get payment requirements with price metadata, pay on-chain, and retry automatically.

Do I have to use MCP?
Yes.

Who is MCPay for?

Providers who want to monetize per-call access to their APIs/tools.
Agents/Integrators who need programmatic, per-request payments without API keys or subscriptions.
Builders who want the fastest path to ship a paid MCP server.

What’s the MCPay Registry?
A public catalog of MCP servers and their priced tools. It shows metadata, usage stats, and integration snippets. Browse at Servers.

How it works

What is x402 and the 402 flow?

Client calls a protected route/tool.
Service responds with 402 and metadata (asset, amount, destination, memo, expiry).
Client (or MCPay proxy/SDK) pays on-chain.
Request is retried with payment proof.
Response succeeds.

Is this “Stripe for agents”?
It has a similar goal — enabling monetization — but different mechanics: no API keys, no subscriptions, no dashboards. It’s pay-per-call at protocol level, natively understood by agents.

Can humans also pay?
Yes. If the request comes from a browser, wallet extensions or embedded wallets can complete the same 402 payment flow.

Pricing & Business

What pricing models are supported?

Flat per call (default).
Tiered or per-tool pricing.
Dynamic pricing coming soon

Does MCPay take a cut?
No by default — payments are routed directly to your wallet. If you use managed wallets or optional hosted features, platform fees may apply.

Do you support revenue splits?
Splits can be implemented by emitting multiple accepted destinations in 402 metadata, or handled off-chain. Native splits are on the roadmap. coming soon

Payments, Wallets & Chains

Which chains/tokens are supported?

Stablecoins (like USDC) on all supported networks.

Currently supported EVM networks: base-sepolia, base, avalanche-fuji, avalanche, iotex, sei, sei-testnet, polygon, polygon-amoy

Solana and other SVM networks: solana-devnet, solana

What wallets can be used?

EOAs via private key (for dev/test).
CDP/embedded wallets (better UX).
Browser wallets for humans.

How do I cap spend?
Set maxPaymentValue in the SDK (denominated in base units, e.g. 6 decimals for USDC). This ensures per-call spend cannot exceed a limit.

Security & Reliability

Do you store private keys?

In SDK mode, keys remain on your server/client.
With managed wallets, keys stay with the wallet provider; MCPay only verifies proofs.

Rate limits & DoS?
The proxy includes basic rate limiting, header scrubbing, and GET caching. Standard API security (WAF, throttling) is still recommended.

SDK, CLI & DevEx

Which languages are supported?
Official TypeScript SDK + CLI. Any language can integrate by handling 402 and sending back an X-PAYMENT proof.

How do I integrate quickly?
With the CLI:

npx mcpay server --urls https://mcpay.tech/mcp/<id> --private-key 0xYOUR_KEY

How do I define paid tools in code?

Check the SDK here

import { createMcpPaidHandler } from "mcpay/handler"

export const paidMcp = createMcpPaidHandler(
  async (server) => {
    server.paidTool(
      "hello",
      "say hello",
      "$0.001",
      {},
      async () => ({ content: [{ type: "text", text: "Hello, world!" }] })
    )
  },
  {
    recipient: { evm: { address: "0xYOUR_ADDRESS" } }
  }
)

Legal

Are you affiliated with the APIs I wrap?

No. MCPay is an integration layer. Wrapped APIs remain independent and subject to their own terms.

FAQ