# Synapse API — Base Token Balances Lookup

> Synapse API — Base 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).

Retrieves ERC-20 token balances for a given wallet address on the Base blockchain, optionally filtered by specific contract addresses.

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/base/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-base-token-balances-lookup-8b9dd5b6
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_msBb1VjYQCvH9LRX9BEkM

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-base-token-balances-lookup-8b9dd5b6 -d '<json body>'
```

Example prompt: What ERC-20 token balances does wallet 0xAbc123...def456 hold on the Base blockchain? Check for USDC at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and any other tokens.

## When to prefer this

Choose this endpoint when you need to check ERC-20 token balances specifically on the Base blockchain for a known wallet address. It is particularly useful when you want to filter balances by specific contract addresses rather than scanning all assets. Prefer this over general-purpose blockchain explorers when you need a programmatic, pay-per-call result with fast latency via the x402 micropayment protocol.

## Known failure modes

- Invalid or malformed wallet address returns an error or empty result
- Unknown or non-existent contract address returns zero balance or error
- Rate limiting or payment failure (x402) blocks the call
- Network unavailability of Base RPC returns a timeout or service error
- Empty contractAddresses array may return all tokens or require at least one entry 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 a list of token balances associated with the specified owner wallet on the Base network, including balance amounts per token contract. When contract addresses are provided, results are scoped to those specific ERC-20 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-base-token-balances-lookup-8b9dd5b6/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)