Multi-chain EVM RPC (read-only)

Read-only JSON-RPC against Ethereum, Base, Polygon, Arbitrum, or Optimism with built-in multi-endpoint failover - one paid call, no node or API key of your own. Send POST /api/evm-rpc with the required field method and pay $0.004 per call over x402 or MPP (there is no free tier). It returns a JSON object with network, method and result.

Prefer the named reads (block-number, chain-info, block-info, event-logs, erc721-owner, contract-code) for common tasks - they validate inputs and cost less; use this when you need a whitelisted method they do not wrap. Whitelisted methods only: eth_blockNumber, eth_gasPrice, eth_getBalance, eth_getTransactionCount, eth_getBlockByNumber, eth_getTransactionByHash, eth_getTransactionReceipt, eth_call, eth_getCode, eth_getStorageAt, eth_chainId, eth_feeHistory, net_version. Mutating, signing, subscription, and unbounded methods (eth_getLogs) are rejected. Results over 200KB serialized return 413 - narrow the query.

Category: Crypto & onchain data · Tags: crypto rpc json-rpc evm multichain base ethereum polygon · Also found as: rpc

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Parameters

Example request

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

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

Example response

{
  "network": "base",
  "method": "eth_blockNumber",
  "result": "0x1a2b3c4"
}

From an MCP client

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

The hosted connector at https://agent402.tools/mcp needs a payment for evm-rpc; 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/evm-rpc 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/evm-rpc", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "network": "base",
    "method": "eth_blockNumber",
    "params": []
  }),
});

Part of these workflows

Multi-chain EVM RPC (read-only) is one step in this skill pack, each sold as a single call:

• Transaction forensics - Explain what an EVM transaction actually did: confirmation status, the raw transaction from the chain, decoded calldata with typed parameters, the resolved function signature, and labeled counterparties.

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