MEV block payment lookup

Look up the MEV-Boost payment for a specific slot or block number via the Flashbots relay. Returns the builder, proposer, value paid in ETH, gas usage, and tx count. Returns found=false if the block was built locally or via a different MEV-Boost relay (Flashbots is one of several).

Input

Field	Type	Description
slot	number	Beacon chain slot number (one of slot/blockNumber required).
blockNumber	number	Execution layer block number (one of slot/blockNumber required).

Example output

{
  "found": true,
  "slot": 12345678,
  "blockNumber": 22000000,
  "blockHash": "0xabc...",
  "builderPubkey": "0x9000...",
  "builderShort": "0x90000000…abcdef",
  "proposerPubkey": "0xa000...",
  "proposerFeeRecipient": "0x1234...",
  "valueWei": "72345000000000000",
  "valueEth": 0.072345,
  "gasUsed": 14987654,
  "gasLimit": 30000000,
  "numTx": 187,
  "relay": "flashbots"
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/mev-block-payment \
  -H "Content-Type: application/json" \
  -d '{"blockNumber":22000000}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

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

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/mev-block-payment", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "blockNumber": 22000000
  }),
});

Wallet-only. This tool reaches the network/browser/storage, so it is paid in USDC via x402 (no proof-of-work tier).

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