Wallet balance (native + ERC-20)

Look up the native coin balance (ETH/MATIC) plus every ERC-20 holding for a wallet address on Ethereum, Base, Polygon, Arbitrum, or Optimism. Send POST /api/wallet-balance with the required field address and pay $0.002 per call over x402 or MPP (there is no free tier). It returns a JSON object with address, network, native and tokens.

Returns clean decimal balances (already scaled by token decimals) plus symbol and contract - ready to display in a UI or feed into a portfolio tool.

Category: Crypto & onchain data · Tags: crypto wallet balance erc20 evm base ethereum token · Also found as: balance live-balance eth_getbalance

TRY IN PLAYGROUND →

Parameters

Example request

curl -i -X POST https://agent402.tools/api/wallet-balance \
  -H "Content-Type: application/json" \
  -d '{"address":"0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0","network":"base"}'

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

Example response

{
  "address": "0xabf4fabd7c416fb67202e5f9002389fc75e2a9d0",
  "network": "base",
  "native": {
    "symbol": "ETH",
    "balance": "0.001234",
    "raw": "1234000000000000"
  },
  "tokens": [
    {
      "contract": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
      "symbol": "USDC",
      "decimals": 6,
      "balance": "100",
      "raw": "100000000"
    }
  ]
}

From an MCP client

catalog.call {
  "slug": "wallet-balance",
  "params": {
    "address": "0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0",
    "network": "base"
  }
}

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

Errors and behavior

• address 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/wallet-balance 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/wallet-balance", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "address": "0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0",
    "network": "base"
  }),
});

Part of these workflows

Wallet balance (native + ERC-20) is one step in these 2 skill packs, each sold as a single call:

• NFT portfolio - NFT + wallet snapshot: NFT holdings, native balance, and ETH price for a given address in one call.
• Wallet audit - Full wallet activity review: balance, recent transactions, and token metadata for a given address.

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