Read-only JSON-RPC passthrough

Escape hatch for power users: forward an arbitrary read-only JSON-RPC method to the chain. Send POST /api/eth-call with the required field method and pay $0.002 per call over x402 or MPP (there is no free tier). It returns a JSON object with network, method and result.

Method must be in our read-only whitelist (eth_call, eth_getLogs, eth_getBlockByNumber, eth_getTransactionReceipt, eth_chainId, eth_blockNumber, etc.). Mutating methods (eth_sendTransaction, eth_sendRawTransaction) are rejected - sign and broadcast through your own provider.

Category: Crypto & onchain data · Tags: crypto rpc json-rpc evm eth-call advanced · Also found as: call eth_call

TRY IN PLAYGROUND →

Parameters

Example request

curl -i -X POST https://agent402.tools/api/eth-call \
  -H "Content-Type: application/json" \
  -d '{"method":"eth_blockNumber","params":[],"network":"base"}'

Without payment this returns HTTP 402 Payment Required with the exact price for eth-call; any x402 v2 or MPP client pays it and retries.

Example response

{
  "network": "base",
  "method": "eth_blockNumber",
  "result": "0x1234567"
}

From an MCP client

catalog.call {
  "slug": "eth-call",
  "params": {
    "method": "eth_blockNumber",
    "params": [],
    "network": "base"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for eth-call; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• method is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/eth-call returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

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();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/eth-call", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "method": "eth_blockNumber",
    "params": [],
    "network": "base"
  }),
});

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