# Synapse API — Arbitrum RPC Endpoint

> Synapse API — Arbitrum RPC Endpoint 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).

Provides JSON-RPC access to the Arbitrum blockchain network via a pay-per-call proxy.

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/arbitrum/rpc
- 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-arbitrum-rpc-endpoint-e4e155f3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_K4YndiZ34uOYd2uVl48p8

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-arbitrum-rpc-endpoint-e4e155f3 -d '<json body>'
```

Example prompt: Call eth_getBalance on the Arbitrum network for address 0xAbC...123 and tell me how much ETH it holds.

## When to prefer this

Choose this endpoint when you need pay-per-call access to the Arbitrum network without managing your own RPC node or committing to a subscription. Ideal for AI agents that interact with Arbitrum sporadically and want micropayment billing via x402/USDC rather than a monthly API key plan.

## Known failure modes

- Invalid JSON-RPC method name returns error code -32601 (method not found)
- Malformed params array causes -32602 (invalid params)
- Payment not included or insufficient USDC returns 402 Payment Required
- Network congestion or node unavailability returns 503 or timeout
- Calling a write method (eth_sendRawTransaction) without a signed transaction returns execution error

## 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 standard JSON-RPC response object from the Arbitrum node, including result data (e.g. balance in hex, block object, transaction receipt) or an error object with code and message if the call fails.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "method": {
   "type": "string"
  },
  "params": {
   "type": "array",
   "items": {}
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synapse-api-arbitrum-rpc-endpoint-e4e155f3/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)