JSON-RPC reference

# read balance
curl -sS https://YOUR-GATEWAY-DOMAIN/rpc/ethereum \
  -H "Authorization: Bearer cs_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getBalance","params":["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","latest"]}'

# broadcast a transaction you signed yourself (ChainBridge never signs on your behalf)
curl -sS https://YOUR-GATEWAY-DOMAIN/rpc/ethereum \
  -H "Authorization: Bearer cs_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":2,"method":"eth_sendRawTransaction","params":["0x02f8..."]}'

const CS_KEY = process.env.CS_API_KEY;   // cs_live_xxx — server side only
const ENDPOINT = 'https://YOUR-GATEWAY-DOMAIN/rpc/ethereum';

async function rpc(method, params = [], attempt = 1) {
  const res = await fetch(ENDPOINT, {
    method: 'POST',
    headers: { 'Authorization': `Bearer ${CS_KEY}`, 'Content-Type': 'application/json' },
    body: JSON.stringify({ jsonrpc: '2.0', id: Date.now(), method, params })
  });

  const requestId = res.headers.get('X-Request-Id');

  // rate limited: back off for the server-provided seconds, retry at most 3 times
  if (res.status === 429 && attempt <= 3) {
    const wait = Number(res.headers.get('Retry-After') || 5);
    await new Promise((r) => setTimeout(r, wait * 1000));
    return rpc(method, params, attempt + 1);
  }

  const payload = await res.json();
  if (payload.error) {
    // node error: keep requestId for troubleshooting; failed requests are not billed
    throw new Error(`RPC failed (${payload.error.code}): ${payload.error.message}, request id ${requestId}`);
  }
  return payload.result;
}

const height = await rpc('eth_blockNumber');
console.log('Current block height (hex):', height);

import os
import requests

CS_KEY = os.environ["CS_API_KEY"]        # cs_live_xxx — server side only
URL = "https://YOUR-GATEWAY-DOMAIN/rpc/ethereum"

# batch array: each element is billed its own CU (metered per item)
batch = [
    {"jsonrpc": "2.0", "id": 1, "method": "eth_chainId", "params": []},
    {"jsonrpc": "2.0", "id": 2, "method": "eth_blockNumber", "params": []},
    {"jsonrpc": "2.0", "id": 3, "method": "eth_getBalance",
     "params": ["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045", "latest"]},
]

resp = requests.post(
    URL,
    json=batch,
    headers={"Authorization": f"Bearer {CS_KEY}"},
    timeout=15,
)
for item in resp.json():
    if "error" in item:
        print(f"item {item['id']} failed: {item['error']['message']}")
    else:
        print(f"item {item['id']} result: {item['result']}")