Context

{
  "context": {
    "citations": [
      {
        "excerpt": "x402 enables HTTP-native payments for APIs and agents.",
        "excerpt_sha256": "0000000000000000000000000000000000000000000000000000000000000000",
        "id": "c1",
        "locator": "p[2]"
      }
    ],
    "estimated_tokens_saved": 1200,
    "markdown": "# Welcome to x402\n\n## c1 · p[2]\n\nx402 enables HTTP-native payments for APIs and agents.",
    "raw_token_estimate": 1250,
    "returned_token_estimate": 50,
    "token_estimate_method": "characters_divided_by_4"
  },
  "context_id": "ctx_0123456789abcdef",
  "delivery": {
    "cache_status": "miss",
    "cost_class": "fresh_static",
    "currency": "USDC",
    "economics": {
      "estimate_basis": "configured_route_estimate",
      "estimated_gross_margin": 0.8,
      "estimated_gross_profit_usd": 0.004,
      "estimated_variable_cost_usd": 0.001
    },
    "generated_at": "2026-01-01T00:00:00.250Z",
    "latency_ms": 250,
    "network": "eip155:8453",
    "payment": {
      "failed_delivery_charge_policy": "not_settled_when_handler_status_is_400_or_higher",
      "protocol": "x402",
      "settlement_receipt_header": "PAYMENT-RESPONSE",
      "settlement_status": "reported_in_response_header",
      "verification_status": "verified"
    },
    "price_usd": 0.005,
    "route": "public_html_direct",
    "status": "delivered"
  },
  "receipt_id": "rcpt_01234567-89ab-cdef-0123-456789abcdef",
  "safety": {
    "prompt_injection_signals": [],
    "public_source_only": true,
    "robots_policy": "allowed",
    "shared_cache_eligible": true,
    "source_directives": []
  },
  "schema_version": "context-receipt.v1",
  "source": {
    "canonical_url": "https://docs.cdp.coinbase.com/x402/welcome",
    "content_sha256": "0000000000000000000000000000000000000000000000000000000000000000",
    "content_type": "text/html; charset=utf-8",
    "fetched_at": "2026-01-01T00:00:00.000Z",
    "final_url": "https://docs.cdp.coinbase.com/x402/welcome",
    "requested_url": "https://docs.cdp.coinbase.com/x402/welcome",
    "title": "Welcome to x402"
  },
  "transformation": {
    "max_tokens": 2000,
    "method": "deterministic_extract",
    "model_used": false,
    "pipeline_version": "html-deterministic.v1",
    "question": "What is x402 designed to enable for agents and APIs?"
  }
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://context-relay.contextrelay.workers.dev/api/v1/context' \
  -H 'content-type: application/json' \
  --data-raw '{"max_price_usd":0.005,"max_tokens":2000,"question":"What is x402 designed to enable for agents and APIs?","url":"https://docs.cdp.coinbase.com/x402/welcome"}'

# 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://context-relay.contextrelay.workers.dev/api/v1/context' \
  -H 'content-type: application/json' \
  --data-raw '{"max_price_usd":0.005,"max_tokens":2000,"question":"What is x402 designed to enable for agents and APIs?","url":"https://docs.cdp.coinbase.com/x402/welcome"}' \
  | 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 $0.005 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.005" });
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 $0.005 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fcontext-relay.contextrelay.workers.dev%2Fapi%2Fv1%2Fcontext&method=POST
const res = await pay("https://context-relay.contextrelay.workers.dev/api/v1/context", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "max_price_usd": 0.005,
    "max_tokens": 2000,
    "question": "What is x402 designed to enable for agents and APIs?",
    "url": "https://docs.cdp.coinbase.com/x402/welcome"
  }),
});
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 $0.005 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.005"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://context-relay.contextrelay.workers.dev/api/v1/context",
        json={
            "max_price_usd": 0.005,
            "max_tokens": 2000,
            "question": "What is x402 designed to enable for agents and APIs?",
            "url": "https://docs.cdp.coinbase.com/x402/welcome",
        },
    )
    print(res.status_code, res.text)