# Synapse API — Token Balances Lookup

> Synapse API — Token Balances Lookup 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 2026-09-15).

Fetches token balances for a given wallet address across specified ERC-20 contract addresses on supported blockchain networks

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/bob/token/balances
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-token-balances-lookup-645eae9a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UUtSbVXPAS3SEPfWFPoL9

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-token-balances-lookup-645eae9a -d '<json body>'
```

Example prompt: What are the token balances for wallet 0xABC...123 for the contracts 0xToken1 and 0xToken2?

## When to prefer this

Use this endpoint when you need to programmatically check on-chain ERC-20 token balances for a specific wallet address across one or more contract addresses, especially when integrating into a pay-per-call agent workflow via x402. Prefer this over general blockchain explorers when you need machine-readable balance data without manual lookup.

## Known failure modes

- Invalid or malformed wallet address returns an error or empty result
- Invalid contract addresses return zero balances or errors
- Network congestion or RPC node issues may delay or fail responses
- Unsupported blockchain network for the given contract may return null
- Missing required 'owner' field causes a 400 bad request

## 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 the token balances held by the specified wallet owner address for each of the provided ERC-20 contract addresses, likely including token amounts and possibly token metadata per contract.

## 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-token-balances-lookup-645eae9a/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)