x402 · pay-per-call · no API keys

Data your agent can buy per call.

An agent asks, gets a 402 with a price, pays a fraction of a cent in USDC and retries. It doesn't need an account, a key or a plan. Providers are paid on every call.

Browse the catalog → Connect an agent

$ curl -i "https://fourzerotwo.si/v1/uk-postcodes/lookup?postcode=SW1A+1AA"
HTTP/2 402 Payment Required
payment-required: eyJ4NDAyVmVyc2lvbiI6Miwi…
  → amount 2000 (= $0.002 USDC) · network base · payTo 0xc176…B84B

# agent wallet signs a gasless USDC authorisation
$ curl "https://fourzerotwo.si/v1/uk-postcodes/lookup?postcode=SW1A+1AA" -H "payment-signature: eyJ…"
HTTP/2 200 OK
payment-response: {"success":true,"transaction":"0x9f3a…e1"}
{"result":{"postcode":"SW1A 1AA","latitude":51.50101,
  "admin_district":"Westminster","region":"London", …}}

uk-bank-holidays/all $0.001 uk-gazette/deceased-estates $0.01 uk-gazette/notice $0.02 uk-postcodes/lookup $0.002 uk-postcodes/nearest $0.002

5paid endpoints

3categories

0paid calls settled

0API keys issued

Catalog

Every API is a URL and an MCP tool.

You pay per call and nothing else. If the data source fails, you aren't charged.

calendarfrom $0.001

UK Bank Holidays

Official bank holidays for England & Wales, Scotland and Northern Ireland.

1 endpoint →

legalfrom $0.01

UK Gazette Estates

Search UK deceased-estates (probate) notices from The Gazette and pull structured notice detail.

2 endpoints →

geofrom $0.002

UK Postcodes

Geocode and describe any UK postcode: coordinates, district, ward, constituency, region.

2 endpoints →

Search all endpoints →

For agents

How a paid call works

Ask

Call any endpoint, or its tool on the MCP server.

402

The response carries the price, network and recipient as x402 requirements.

Sign

The agent's wallet signs a USDC transfer authorisation. It needs no gas.

200

We verify the payment, fetch the data, settle on-chain, then return it.

MCP

One server, every API. An unpaid tool call returns x402 requirements, and x402-capable clients pay through _meta["x402/payment"].

{
  "mcpServers": {
    "fourzerotwo": { "type": "http", "url": "https://fourzerotwo.si/mcp" }
  }
}

HTTP

Any x402 client works. With Coinbase's @x402/fetch:

const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:*",
              client: new ExactEvmScheme(account) }],
});
await pay("https://fourzerotwo.si/v1/uk-gazette/deceased-estates?name=…");

Sell your data

Got data? Get paid per call.

Point us at an existing API, or upload a spreadsheet and we host it as one. We handle the 402s, payment checks, settlement, MCP tools and getting listed where agents look. Payments go straight to your wallet, and we never hold your money.

List your API →

# what a listing looks like
provider:  Your Company
api:       uk-garages
endpoint:  GET /v1/uk-garages/search?town=Margate
price:     $0.005 / call
payTo:     0xYourWallet…
listed:    MCP · Bazaar · llms.txt · catalog.json