Research Brief

{
  "brief": {
    "caveats": [
      "Ecosystem evolving quickly; always check live facilitator docs"
    ],
    "confidence": 0.78,
    "headline": "x402 turns HTTP 402 into USDC micropayments for agents",
    "key_points": [
      "Server returns 402 with payment terms; client pays and retries",
      "CDP Facilitator commonly used for verify/settle on Base",
      "Bazaar indexes discoverable paid routes"
    ],
    "summary": "x402 is an open payment protocol that uses HTTP 402 Payment Required so clients (including AI agents) can pay for web resources with stablecoins, commonly USDC on Base, via a facilitator that verifies and settles."
  },
  "citations": [
    {
      "published": null,
      "publisher": "Coinbase CDP",
      "snippet": "The x402 Bazaar is a catalog of payment-gated services discovered by the CDP Facilitator.",
      "title": "x402 Bazaar (Discovery Layer)",
      "url": "https://docs.cdp.coinbase.com/x402/buyer/discover-services"
    }
  ],
  "client_ref": null,
  "endpoint": "research-brief",
  "ok": true,
  "usage": {
    "floor_mult": 1.3,
    "latency_ms": 6400,
    "price_usdc": "0.08",
    "sources_used": 3,
    "token_cost_est_usdc": "0.05"
  }
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://x402.hydratrader.ai/v1/research-brief' \
  -H 'content-type: application/json' \
  --data-raw '{"depth":"quick","question":"What is the x402 protocol and how do agents pay for APIs?","scope":{"max_sources":3}}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://x402.hydratrader.ai/v1/research-brief' \
  -H 'content-type: application/json' \
  --data-raw '{"depth":"quick","question":"What is the x402 protocol and how do agents pay for APIs?","scope":{"max_sources":3}}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.08 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.08" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.08 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fx402.hydratrader.ai%2Fv1%2Fresearch-brief&method=POST
const res = await pay("https://x402.hydratrader.ai/v1/research-brief", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "depth": "quick",
    "question": "What is the x402 protocol and how do agents pay for APIs?",
    "scope": {
      "max_sources": 3
    }
  }),
});
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.08 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.08"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://x402.hydratrader.ai/v1/research-brief",
        json={
            "depth": "quick",
            "question": "What is the x402 protocol and how do agents pay for APIs?",
            "scope": {
                "max_sources": 3,
            },
        },
    )
    print(res.status_code, res.text)