# Base Token Facts API – Wallet Lookup

> Base Token Facts API – Wallet Lookup is a paid API for AI agents from base-facts.yankii.fr, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-11).

Returns on-chain ETH balance, USDC balance, nonce, contract status, and current block number for a given Base mainnet wallet address.

## Facts

- Endpoint: POST https://base-facts.yankii.fr/v1/wallet?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-token-facts-api-wallet-lookup-43869d26
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tKGVKjQnfB7PPS_VsEMs4

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-token-facts-api-wallet-lookup-43869d26 -d '<json body>'
```

Example prompt: What's the ETH and USDC balance for wallet 0x1234...abcd on Base mainnet, and is it a smart contract?

## When to prefer this

Use this endpoint when you need a quick, atomic snapshot of a Base mainnet wallet's ETH and USDC balances plus contract status in a single call, without running your own RPC node. Prefer it over general Ethereum RPC calls when you specifically need Base-chain data with a pay-per-call micropayment model via x402.

## Known failure modes

- Invalid or malformed address (not 0x-prefixed or wrong length) — likely returns a 400 or error JSON
- Address not found on Base mainnet — returns zero balances and nonce 0
- RPC node unavailable or timeout — may return 5xx or connection error
- Network congestion causing stale block number data
- Payment failure via x402 protocol — 402 response if USDC payment not completed

## How this service works

Get ETH and USDC balance for a wallet address

## Output

A JSON object containing the wallet's ETH balance in both wei and human-readable decimal, USDC balance in atomic units and decimal, the account nonce, a boolean indicating whether the address is a contract, the block number at which the data was fetched, and the RPC source identifier (base-mainnet-rpc).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "address": {
   "type": "string",
   "description": "0x-prefixed address"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "eth": {
   "wei": "0",
   "decimal": "0.0"
  },
  "usdc": {
   "atomic": "0",
   "decimal": "0.000000"
  },
  "nonce": 0,
  "source": "base-mainnet-rpc",
  "isContract": false,
  "blockNumber": "52130000"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-token-facts-api-wallet-lookup-43869d26/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-facts.yankii.fr](https://www.zero.xyz/host/base-facts.yankii.fr/llms.txt)