curl -X GET '/v1/agent/balance?wallet_id=aw_01abc123' \
  -H 'Authorization: Bearer yac_connector_api_key'

{
  "success": true,
  "data": {
    "wallet_id": "aw_01abc123",
    "wallet_address": "0x742d35Cc6634C0532925a3b8D4C9C2A5Ef8C2B1",
    "chain": "base",
    "balance": 250.00,
    "assets": {
      "USDC": 250.00
    }
  }
}