# Synapse API — zkSync Token Balances

> Synapse API — zkSync 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 2026-09-13).

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

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/zksync/token/balances
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-zksync-token-balances-f2f6195f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_sbdLYt3SiWShYT7R-38UX

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-zksync-token-balances-f2f6195f -d '<json body>'
```

Example prompt: Check all the ERC-20 token balances for wallet address 0xAbC123...def on zkSync — also filter by these contract addresses: 0xToken1 and 0xToken2.

## When to prefer this

Choose this endpoint when you specifically need token balances on the zkSync Layer 2 network. It supports pay-per-call via x402 (no API key setup needed), making it ideal for autonomous agents that need on-demand zkSync balance lookups without a subscription. Prefer this over general Ethereum balance APIs when zkSync-native data is required.

## Known failure modes

- Invalid or malformed wallet address returns an error or empty result
- Non-existent or non-ERC-20 contract addresses may return zero balances or errors
- zkSync RPC unavailability causes timeout or 5xx error
- Payment failure via x402 protocol blocks the request
- Rate limiting if called too frequently

## 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 owner on the zkSync network, including token amounts for each queried contract address or all held tokens if no contracts are specified.

## 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-zksync-token-balances-f2f6195f/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)