Transaction Explainer + Payment Check

Explain a Base or Ethereum transaction in plain JSON and check that a payment arrived.

Give a transaction hash and get status, block time, confirmations, sender and recipient, ETH value, gas fee (including the Base L1 fee), the method name, and every ERC-20 and NFT transfer with token symbols and human amounts. Add expect_to, expect_token and expect_amount to confirm that a USDC or ETH payment reached the right address. Public RPC data only.

$0.0025 per call in USDC on Base via x402, or pay by card with prepaid credits (2 credits) · 1 free call per caller · no signup · Verified on PayAPI Market (one settled test payment by PayAPI Market: $0.001 on GET /api/tx-explain, 2026-10-25, tx; not an audit or uptime guarantee)

GET https://freetier-agent-api.pages.dev/api/tx-explain

When to use it

Use tx-explain to understand one transaction or to verify a payment (USDC, ETH, any ERC-20) before delivering goods. Use wallet-profile for an address, contract-abi for a contract interface and token-risk to judge a token.

Parameters

Example output (real response, trimmed)

{
 "chain": "base",
 "status": "success",
 "confirmations": 120000,
 "from": "0x...",
 "to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
 "method": {
  "selector": "0xe3ee160e",
  "signatures": [
   "transferWithAuthorization(address,address,uint256,uint256,uint256,bytes32,uint8,bytes32,bytes32)"
  ]
 },
 "feeEth": "0.0000012",
 "transfers": [
  {
   "standard": "erc20",
   "symbol": "USDC",
   "amount": "0.001",
   "from": "0x...",
   "to": "0x165eb3dc3e98403ecb1141e90400f5e71806554b"
  }
 ],
 "paymentCheck": {
  "matched": true
 }
}

Try it

Free call (no wallet needed)

curl -s "https://freetier-agent-api.pages.dev/api/tx-explain?hash=0xad06b77208318128017ce69952685e3f242281202d7cc9d50847619a706d2d7f&chain=base"

Pay by card (no wallet): prepaid credits

Buy a credit pack on Gumroad (1,000 credits $3), then send your license key. The X-Credits-Remaining response header shows your balance; failed calls are not charged.

curl -s "https://freetier-agent-api.pages.dev/api/tx-explain?hash=0xad06b77208318128017ce69952685e3f242281202d7cc9d50847619a706d2d7f&chain=base" \
  -H 'X-License-Key: YOUR-LICENSE-KEY'

JavaScript / TypeScript (@x402/fetch)

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY); // wallet with USDC on Base
const fetchWithPayment = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});
const res = await fetchWithPayment("https://freetier-agent-api.pages.dev/api/tx-explain?hash=0xad06b77208318128017ce69952685e3f242281202d7cc9d50847619a706d2d7f&chain=base");
console.log(await res.json());

Python (x402 + httpx)

# pip install "x402[httpx,evm]" eth-account
import asyncio, os
from eth_account import Account
from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

async def main():
    client = x402Client()
    register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))
    async with x402HttpxClient(client) as http:
        r = await http.get("https://freetier-agent-api.pages.dev/api/tx-explain?hash=0xad06b77208318128017ce69952685e3f242281202d7cc9d50847619a706d2d7f&chain=base")
        print(r.json())

asyncio.run(main())

A bare request without parameters returns the HTTP 402 payment challenge (x402 v2 in the PAYMENT-REQUIRED header, v1 in the body). Invalid input gets a 400 before any payment.

Billing policy

Failed calls are never charged. Failed calls are never charged: the payment is verified first, the request runs, and the payment is settled only if it succeeded. Errors (4xx/5xx) are not settled, and invalid input is rejected before any payment or free call.

Uptime and latency

Independent monitoring of this endpoint: 402index service page (health, 30-day uptime, p50 latency).

Also available as

• MCP tool tx_explain at https://freetier-agent-api.pages.dev/mcp (Streamable HTTP; in-band x402 payment via _meta["x402/payment"], or card credits via the X-License-Key header)
• OpenAPI 3.1 with the full output JSON Schema

Agent Extraction API by FreeTier Kits · Terms · llms.txt · /.well-known/x402 · MCP: https://freetier-agent-api.pages.dev/mcp · Contact: tec@mail.grokbot.com
This site and its texts were written with AI assistance and reviewed for accuracy; example outputs are real responses from the API.