For AI Agents

One MCP endpoint at payapi.market/mcp. Search, list and get are free. 282 live APIs, 266 settlement-verified, paid per call in USDC on Base.

Last updated: 2026-10-06

The MCP endpoint

Discovery is free. Agents search the catalogue here. Payment happens on the listing 402, not on PayAPI.

url https://payapi.market/mcp

Connecting from Claude Desktop

Add this to your claude_desktop_config.json:

{
  "mcpServers": {
    "payapi": {
      "url": "https://payapi.market/mcp"
    }
  }
}

Restart Claude Desktop. You get three discovery tools: search_apis, list_apis and get_api. Discovery is free; paying happens on the listing's own 402, called directly against the provider.

Separately and optionally, our own UK property tools live on a different first-party server, https://web-production-18a32.up.railway.app/mcp/sse, whose tools/call is paid. It exposes those tools only, not the marketplace catalogue.

Connecting from Cursor / Continue / custom agents

Any MCP-compatible client works. Point it at the same URL above, https://payapi.market/mcp, which is stateless streamable HTTP and not SSE. In a chat client you can simply paste these three lines:

Connect to the PayAPI Market MCP at https://payapi.market/mcp
Search verified APIs for text metrics
Open the listing the tool returns

A worked example of what happens next, through to the on-chain receipt, is at how an agent finds PayAPI.

Paying for calls

Your client needs to:

1. Have a USDC wallet on Base with a small balance
2. Handle HTTP 402 responses by signing and broadcasting the requested payment
3. Retry the request with proof of payment

The official x402 client libraries (TypeScript, Python, Rust) handle this automatically. Total per-call latency including payment is ~500-800ms.

Why this matters for agents

Subscription APIs are unusable for agents. You don't know in advance whether you'll need 5 calls or 50,000, you can't sign up for a $99/month plan when each user session might justify $0.02 of API spend, and you can't manage 50 different API keys across 50 different vendors. PayAPI Market collapses all of that into a single MCP endpoint and a USDC wallet.

Frequently asked questions

Do I really not need an API key?

Correct. With x402 the payment is the authentication. The provider's endpoint replies HTTP 402 with the price and wallet, your agent signs a USDC payment authorisation, and the request is retried with it attached. The provider's facilitator settles it on Base, so your agent needs no API key, no account and no ETH for gas.

What does a call cost?

Each provider sets its own price per call, and the listing shows it. Prices start at fractions of a cent, and some specialist routes cost more. The exact USDC amount also arrives in the 402 challenge before any money moves, so your agent can check the price and refuse anything above its cap.

Which wallet should my agent use?

Any EVM wallet that holds USDC on Base, such as Coinbase Wallet, MetaMask or your agent's own key. Use a dedicated wallet with a small balance, for example $5. An x402 client library such as @x402/fetch for JavaScript or the x402 package for Python signs each payment for you.

How do I use PayAPI Market from Claude or Cursor?

Add one entry to your MCP config, "mcpServers": { "payapi": { "url": "https://payapi.market/mcp" } }, then restart the client. Your agent gets three free tools: search_apis, list_apis and get_api. To pay for a call, it also needs an x402-capable client and a wallet holding USDC on Base.

Can I cap what my agent spends?

Yes. Every 402 states the exact USDC amount before any money moves, so your agent or x402 client can refuse any call above a per-call limit you set. Fund a dedicated wallet with a small balance, so total spend can never exceed what you put in. There are no subscriptions or recurring charges.

What happens if a call fails after I pay?

PayAPI Market is not in the payment path, so it cannot refund or reverse a payment, and an x402 payment is final once it settles on Base. Many providers settle only after a successful response, but that is each provider's choice. Start with settlement-verified listings and check the reliability score before you call.

Which chains and tokens are supported?

Payments settle in USDC on Base. Every PayAPI Market listing must accept Base USDC on its paid route, and settlement verification happens on Base. Some providers also accept Solana USDC on the same route, which their 402 challenge will show, but that does not change the listing's verified badge.

Is it safe to let an agent pay for APIs?

x402 has no chargebacks, so safety comes from limits you control. Use a dedicated wallet with a small balance, set a per-call price cap, and prefer settlement-verified listings, where PayAPI Market paid a real call and got real product back. Your agent signs each payment itself, and PayAPI Market never holds your funds.