# Synapse API — Token Balances by Owner

> Synapse API — Token Balances by Owner 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).

Returns token balances for a given wallet address across one or more ERC-20 contract addresses on supported blockchain networks

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/adi/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-token-balances-by-owner-6e2cc90f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6kfGByIsfW8MENKut4T0X

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-by-owner-6e2cc90f -d '<json body>'
```

Example prompt: What are the token balances for wallet address 0xABC123... across these contracts: 0xUSDC... and 0xWETH...?

## When to prefer this

Choose this endpoint when you need fast, pay-per-call token balance lookups for one or more ERC-20 contracts on a specific wallet address without managing your own blockchain node infrastructure. It is well-suited for AI agents needing on-demand DeFi portfolio checks, airdrop eligibility verification, or whale monitoring across multiple tokens in a single call.

## Known failure modes

- Invalid owner address format returns an error or empty result
- Unsupported contract address or network returns zero or null balance
- Rate limiting or payment failure (x402) blocks the call
- Network congestion may delay RPC response
- Contract addresses not on a supported chain return no data

## 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 owner wallet for each of the provided contract addresses, including amounts per token contract, enabling portfolio visibility and on-chain asset verification.

## 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-by-owner-6e2cc90f/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)