Tools · data

ETH balance on Base

ETH balance of any address on Base (wei + ETH). Pay-per-call via x402. An empty body is answered for the wallet that pays on Base (the payment's signer); send {"address":"0x…"} for any other address.

$0.001 per call, paid in USDC on Base or Solana with x402 — no account, no API key. POST https://fiatdock.com/v1/chain/eth-balance (or GET with the same fields as query parameters) · MCP tool eth_balance. An answer the tool cannot produce is refused with 4xx/5xx and is not charged.

Inputs

Field	Type	Description	Example
`address`	string	A 40-hex EVM address (0x…). Omit the whole body to get the paying wallet.	`"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"`

Example

Request body

{"address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}

Answer (the published example)

{"network":"base","address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","wei":"1000000000000000000","eth":"1","asOf":"2026-07-30T00:00:00.000Z"}

Call it

curl

# 1) ask: an unpaid call answers 402 with the exact price (free)
curl -i -X POST https://fiatdock.com/v1/chain/eth-balance -H 'content-type: application/json' -d '{"address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}'
# 2) pay: any x402 client signs that 402 and resends — see Node or Python below

Node

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:*", client: new ExactEvmScheme(privateKeyToAccount(process.env.AGENT_PRIVATE_KEY)) }],
});
const r = await pay("https://fiatdock.com/v1/chain/eth-balance", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({"address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}),
});
console.log(r.status, await r.json());

Python

# pip install "x402[httpx,evm]"
import asyncio, json, os
from eth_account import Account
from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm.exact import register_exact_evm_client

async def main():
    client = register_exact_evm_client(x402Client(), Account.from_key(os.environ["AGENT_PRIVATE_KEY"]))
    async with x402HttpxClient(client) as http:
        r = await http.post("https://fiatdock.com/v1/chain/eth-balance", json=json.loads("{\"address\":\"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913\"}"))
        print(r.status_code, r.json())

asyncio.run(main())

MCP (Claude, Cursor, any MCP client)

{"mcpServers":{"fiatdock":{"command":"npx","args":["-y","fiatdock-mcp"],"env":{"AGENT_PRIVATE_KEY":"0x<your agent wallet key>"}}}}
// then call the tool "eth_balance" — the package pays each call from that wallet

The wallet needs USDC on Base. Prefer no install? The remote server https://fiatdock.com/mcp answers the 402 as tool output for an agent that signs its own payments.

Related tools

Machine-readable: OpenAPI · tools.json · llms.txt · /.well-known/x402