# x402 Chain Tools – Native ETH Balance Lookup

> x402 Chain Tools – Native ETH Balance Lookup is a paid API for AI agents from blockchain-api.x402-chain-tools.workers.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Returns the native ETH balance (in both ETH and wei) of a given Base Mainnet wallet address.

## Facts

- Endpoint: POST https://blockchain-api.x402-chain-tools.workers.dev/chain/balance
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-chain-tools-native-eth-balance-lookup-6c2ce53e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7LVFmQf0OYgkNvdC0Aym_

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-chain-tools-native-eth-balance-lookup-6c2ce53e -d '<json body>'
```

Example prompt: What's the current ETH balance for Base wallet address 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045? Give me both the ETH and wei amounts.

## When to prefer this

Use this endpoint when you specifically need the native ETH balance (not ERC-20 tokens) of a Base Mainnet address. Prefer this over generic blockchain explorers when you need a structured JSON response suitable for programmatic use in an agent workflow. Choose the sibling ERC-20 balance endpoint if you need token balances instead.

## Known failure modes

- Invalid address format (not a 0x + 40 hex char string) returns validation error
- Address not found on Base Mainnet (returns balance of 0, not an error)
- RPC node timeout or Base network congestion causes delayed or failed response
- Malformed request body returns 400-level error
- Payment failure (x402) prevents the call from being processed

## How this service works

Get the native ETH balance of a Base address.

## Output

A JSON object containing ok (boolean success flag), the queried address, a balance object with 'eth' (human-readable ETH string) and 'wei' (raw integer string), and the network identifier 'eip155:8453' confirming Base Mainnet.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "address": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$",
   "description": "Base wallet address."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "address": "0x0000000000000000000000000000000000000001",
  "balance": {
   "eth": "0",
   "wei": "0"
  },
  "network": "eip155:8453"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-chain-tools-native-eth-balance-lookup-6c2ce53e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from blockchain-api.x402-chain-tools.workers.dev](https://www.zero.xyz/host/blockchain-api.x402-chain-tools.workers.dev/llms.txt)