MEV builder share

Builder market share aggregated over the last N MEV-Boost blocks via the Flashbots relay. Returns per-builder block count, share percent, total ETH paid to proposers, and average per block. Use to track block-builder concentration or detect a new builder gaining share.

Input

Field	Type	Description
window	number	Recent blocks to aggregate (10-200, default 100).

Example output

{
  "windowBlocks": 100,
  "uniqueBuilders": 5,
  "relay": "flashbots",
  "builders": [
    {
      "builderPubkey": "0x9000...",
      "builderShort": "0x90000000…abcdef",
      "blocks": 42,
      "sharePct": 42,
      "totalEthToProposers": 3.456789,
      "avgEthPerBlock": 0.082305
    }
  ]
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/mev-builder-share \
  -H "Content-Type: application/json" \
  -d '{"window":100}'

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-builder-share", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "window": 100
  }),
});

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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