For AI Agents

One MCP endpoint at payapi.market/mcp. Search, list and get are free. 236 live APIs, 220 settlement-verified, paid per call in USDC on Base.

Last updated: 2026-09-29

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. The whole point of x402 is that authentication and authorisation are bundled into a single payment step. The server returns HTTP 402 with payment requirements, your agent signs and broadcasts the USDC transfer, the request goes through.

What does a typical call cost?

Most APIs on PayAPI Market are priced between $0.0005 and $0.01 per request. A typical agent task uses 2–20 API calls and costs less than a cent in total.

Which wallet should my agent use?

Any USDC-on-Base wallet. The official x402 client libraries handle key management, signing, and broadcasting; you just need to fund a Base address with USDC.

How long does payment add to the request?

Approximately 200–400 ms on top of normal latency, for a total per-call latency of 500–800 ms. Payment is verified in parallel with the request handler when possible.

Can I set a per-call spending cap?

Yes, in your MCP client config. Set max_cost_per_call (in USDC) and the client refuses requests that exceed it.