# Synapse API — Arbitrum Token Balances

> Synapse API — Arbitrum Token Balances is a paid API for AI agents from synapse-api-brown.vercel.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-16).

Fetches ERC-20 token balances for a given wallet address on the Arbitrum network, optionally filtered to specific contract addresses

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/arbitrum/token/balances?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-arbitrum-token-balances-edd0011b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qn3A6eHiwJoLGb1HCxTFy

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 synapse-api-arbitrum-token-balances-edd0011b -d '<json body>'
```

Example prompt: What ERC-20 token balances does wallet 0x742d35Cc6634C0532925a3b844Bc454e4438f44e hold on Arbitrum? Check specifically for USDC (0xFF970A61A04b1cA14834A43f5dE4533eBDDB5CC8) and USDT (0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9).

## When to prefer this

Choose this endpoint when you need to look up ERC-20 token balances for a specific wallet address specifically on the Arbitrum Layer-2 network. It is ideal for DeFi agents, portfolio trackers, and pre-transaction balance checks on Arbitrum. Prefer this over generic blockchain APIs when you need Arbitrum-specific data with pay-per-call pricing and no subscription commitment.

## Known failure modes

- Invalid or malformed wallet address returns an error
- Non-existent or incorrect contract address may return zero balance or an error
- Payment failure via x402 protocol blocks the request
- Arbitrum node unavailability or RPC timeout causes delayed or failed response
- Empty contractAddresses array may return all token balances or nothing depending on implementation

## How this service works

High-speed API suite for AI processing, web scraping, and smart data utilities across 57+ blockchain networks. Pay-per-call via x402.

## Output

Returns token balance data for the specified wallet address on the Arbitrum network, including balance amounts for each ERC-20 token held (optionally filtered to the provided contract addresses). Typically includes token amounts, possibly with token metadata such as symbol and decimals.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "owner": {
   "type": "string"
  },
  "contractAddresses": {
   "type": "array",
   "items": {
    "type": "string"
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synapse-api-arbitrum-token-balances-edd0011b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from synapse-api-brown.vercel.app](https://www.zero.xyz/host/synapse-api-brown.vercel.app/llms.txt)