126 data endpoints your agent buys one call at a time.

Why this exists

When someone asks their agent to find flights to Barcelona next weekend, the agent needs flight data, not a web search that mentions flights. The same goes for a restaurant's reviews, a house listing, a job board, a patent, a product price. Those answers live behind 27 different services and none of them sell a single call to a stranger with a wallet.

Here they all do, at the same price, behind the same two round trips.

How a call works

Any x402 client does this for you — @x402/fetch wraps your existing fetch and the two round trips become one line of code.

A real one

POST /api/v1/google-flights

{
  "departure_id": "MXP",
  "arrival_id": "BCN",
  "outbound_date": "2026-11-14",
  "return_date": "2026-11-16",
  "currency": "EUR"
}

{
  "endpoint": "google-flights",
  "best_flights": [{
    "flights": [{
      "departure_airport": { "id": "MXP", "time": "…" },
      "arrival_airport": { "id": "BCN", "time": "…" },
      "airline": "…", "flight_number": "…",
      "duration": 105
    }],
    "price": 128,
    "total_duration": 105
  }],
  "price_insights": { "lowest_price": 94, … },
  "meta": { "latencyMs": 2100 },
  "paid": { "transaction": "0x…", "network": "eip155:8453" }
}

Responses follow the shape of the source, so the fields differ between endpoints. Every one carries endpoint, meta, attribution and, once paid, paid.transaction. The schema for each is in openapi.json and in its own 402 challenge.

The catalogue

125 endpoints across 19 categories and 27 sources. Machine-readable at /api/v1, which takes ?q= and ?category= and gives each entry a request that works. A handful are follow-ups — they need an identifier from an earlier call, so they sit behind the follow-ups filter and say what they want.

One endpoint that is not a lookup

Paying

USDC on Base or Solana, your pick, same price either way. Your wallet needs only USDC — no ETH and no SOL, because the facilitator pays the network fee on both chains. Every paid response carries the transaction hash that settled it, and a signed offer-receipt if your client asked for one.

import { wrapFetchWithPayment } from "@x402/fetch";

const pay = wrapFetchWithPayment(fetch, wallet);

const res = await pay("https://serp402.com/api/v1/yelp-search", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ find_desc: "ramen", find_loc: "Austin, TX" }),
});
const { paid, ...data } = await res.json();   // paid.transaction is on-chain

From Claude, Cursor or any MCP client

Add the MCP server and your agent gets tools it pays for itself. Fund a wallet with a few dollars of USDC and set a ceiling it cannot be talked past.

{
  "mcpServers": {
    "serp402": {
      "command": "npx",
      "args": ["-y", "serp402-mcp"],
      "env": {
        "SERP402_EVM_PRIVATE_KEY": "0x… a key holding USDC on Base",
        "SERP402_MAX_SPEND_USD": "1.00"
      }
    }
  }
}

Paying from Solana instead? Use SERP402_SOLANA_PRIVATE_KEY (an ed25519 key, hex or base58) in place of the Base one.

You are charged only when you are served

Spending well

Pick the specific endpoint, not the general one

/api/v1/google-flights answers a flight question in one call. A web search for the same thing costs the same and answers it worse.

Read the catalogue first — it is free

/api/v1 gives every path, price and a working example. Guessing an endpoint name is not free.

Filter before you enrich

One /api/v1/google-maps call already returns businesses with rating, phone and website. Apply your criteria there, where it costs nothing.

A 404 means you were not charged

Do not retry it with the same parameters; it will find nothing again.

The version written for the agent rather than for you is at /llms.txt.

Where the data comes from

Public search results, collected through a third-party data provider. Not affiliated with, endorsed by or an official channel of any of the services the results come from. All trademarks and copyright remain the property of their respective owners. Every response carries an attribution object — keep it with the results if you pass them on.