# Base Onchain Balance Checker

> Base Onchain Balance Checker is a paid API for AI agents from onchaincheck.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-29).

Returns the native ETH balance and up to 20 ERC-20 token balances for a given Base wallet address, formatted with symbols and decimals.

## Facts

- Endpoint: GET https://onchaincheck.dev/base/balances?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-onchain-balance-checker-60523845
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bT7783idL-Q0mQ773_FWP

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 base-onchain-balance-checker-60523845
```

Example prompt: What's the current ETH balance and USDC and DEGEN token balances for the Base wallet 0x2211d1D0020DAEA8039E46Cf1367962070d77DA9? The USDC contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and DEGEN is 0x4ed4E862860beD51a9570b96d89aF5E1B0Efefed.

## When to prefer this

Choose this endpoint when you need live, human-readable token balances from the Base network specifically, covering both native ETH and multiple ERC-20s in a single call. It is ideal when you need properly formatted decimals and token symbols without doing your own on-chain RPC calls. Prefer it over generic block explorer APIs when you need structured JSON output for up to 20 tokens simultaneously and are already working within the Base ecosystem.

## Known failure modes

- Invalid wallet address format (non-0x or wrong length) causes a 400 error
- Invalid ERC-20 contract address in the tokens list returns an error or omits that token
- Token contract address is not a valid ERC-20 on Base — may return zero or an error
- More than 20 token addresses provided — rejected by schema validation
- Base network RPC outage causes timeout or 503 response
- Rate limiting or payment failure returns a 402 or 429 response

## How this service works

Native ETH balance of a Base wallet plus the balances of up to 20 ERC-20 tokens you list, formatted with each token's symbol and decimals, read live from Base.

## Output

A JSON object containing the wallet address, the native ETH balance as a decimal string, and an array of token objects each with the contract address, symbol, decimals, raw integer balance, and human-readable decimal balance. All values are read live from Base at call time.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "tokens": {
       "type": "string",
       "pattern": "^(0x[0-9a-fA-F]{40})(,0x[0-9a-fA-F]{40}){0,19}$",
       "description": "Comma-separated ERC-20 contract addresses on Base, up to 20"
      },
      "address": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "Wallet address on Base"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "chain": "base",
  "tokens": [
   {
    "raw": "3528717773",
    "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "symbol": "USDC",
    "balance": "3528.717773",
    "decimals": 6
   },
   {
    "raw": "886309838294787826109722",
    "token": "0x4ed4E862860beD51a9570b96d89aF5E1B0Efefed",
    "symbol": "DEGEN",
    "balance": "886309.838294787826109722",
    "decimals": 18
   }
  ],
  "address": "0x2211d1D0020DAEA8039E46Cf1367962070d77DA9",
  "nativeSymbol": "ETH",
  "nativeBalance": "7.554675633166555733"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-onchain-balance-checker-60523845/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from onchaincheck.dev](https://www.zero.xyz/host/onchaincheck.dev/llms.txt)