# x-402 ERC-20 Multi-Token Balance Checker

> x-402 ERC-20 Multi-Token Balance Checker is a paid API for AI agents from api.x-402.online, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-01).

Returns ETH, USDC, and up to ten ERC-20 token balances for a single Base mainnet address in one call, with decimals resolved and amounts human-readable.

## Facts

- Endpoint: GET https://api.x-402.online/v1/chain/balance?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x-402-erc-20-multi-token-balance-checker-040fa6c3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_YRdrAMxuCRGY64IRqoEUT

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 x-402-erc-20-multi-token-balance-checker-040fa6c3
```

Example prompt: What are the ETH, USDC, and token balances for 0xAbC123...def on Base mainnet — also check these two token contracts: 0xTokenA... and 0xTokenB...?

## When to prefer this

Choose this endpoint when you need ETH plus multiple ERC-20 token balances for a single Base mainnet address in one round trip, with decimals already resolved to human-readable values — eliminating the need to call raw RPC, manage ABI decoding, or make separate balance calls per token. Ideal for AI agents that need a quick portfolio snapshot or pre-flight balance check without setting up a blockchain node or SDK.

## Known failure modes

- Invalid or malformed address returns an error response
- Token contract address is not a valid ERC-20 — balance may be 0 or errored
- More than ten ERC-20 addresses supplied — excess tokens may be ignored or rejected
- Network issues reaching Base mainnet RPC — timeout or 5xx error
- Payment of 0.005 USDC not fulfilled — 402 Payment Required response blocking the call

## How this service works

Get ETH, USDC and up to ten ERC-20 balances of one address in a single call, human-readable. ETH plus USDC plus up to ten ERC-20 balances of one address in a single call, decimals resolved, amounts human-readable. Base mainnet. Query: ?address=0x…&tokens=0x…,0x…

## Output

A single JSON response containing the ETH balance, USDC balance, and balances for each requested ERC-20 token address, all with decimals already resolved and expressed as human-readable decimal amounts (e.g. 1.5 ETH, 200.00 USDC).

## 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",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x-402-erc-20-multi-token-balance-checker-040fa6c3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x-402.online](https://www.zero.xyz/host/api.x-402.online/llms.txt)