# Synapse API — Ethereum Token Balances

> Synapse API — Ethereum 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 2026-09-14).

Retrieves ERC-20 token balances for a given Ethereum wallet address, optionally filtered to specific contract addresses

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/ethereum/token/balances
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-ethereum-token-balances-63807260
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VOz5Lh0N-hGnl_t2ayekB

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-ethereum-token-balances-63807260 -d '<json body>'
```

Example prompt: Check all the ERC-20 token balances held by Ethereum wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045, and specifically look up its USDC balance at contract 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48.

## When to prefer this

Choose this endpoint when you need to look up ERC-20 token balances on the Ethereum mainnet for one or more wallet addresses. It is especially useful for DeFi portfolio tracking, verifying token transfers, and auditing holdings across specific contracts. It covers Ethereum specifically, so prefer it over generic multi-chain endpoints when Ethereum is the target network.

## Known failure modes

- Invalid Ethereum address format returns an error
- Non-existent or zero-balance tokens may return empty results
- Rate limiting or payment failure via x402 protocol blocks the request
- Network timeouts if Ethereum RPC is slow
- Contract addresses that are not valid ERC-20 tokens may return errors or empty balances

## 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 a list of token balances for the specified Ethereum wallet address, each entry indicating the token contract address and the corresponding balance amount held by the owner. If specific contract addresses are provided, results are filtered to those tokens only.

## 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-ethereum-token-balances-63807260/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)