# QuickNode JSON-RPC Proxy — B3 Sepolia

> QuickNode JSON-RPC Proxy — B3 Sepolia is a paid API for AI agents from x402.quicknode.com, paid per call via x402, $10/call, status unknown (last checked 2026-09-14).

Proxies JSON-RPC calls to the B3 Sepolia testnet blockchain via QuickNode's infrastructure

## Facts

- Endpoint: POST https://x402.quicknode.com/b3-sepolia/
- Price: $10/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/quicknode-7cd3a0cf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GyIZKLoh09207SBMBHRaj

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 quicknode-7cd3a0cf -d '<json body>'
```

Example prompt: Can you call eth_getBalance on B3 Sepolia testnet for address 0xAbC123... using QuickNode's RPC proxy and tell me the current balance?

## When to prefer this

Use this endpoint when you need to interact specifically with the B3 Sepolia testnet via a reliable, low-latency RPC provider. Prefer this over self-hosted or free public RPC endpoints when you need consistent uptime and QuickNode's infrastructure. Choose this over other QuickNode sibling endpoints when your target chain is B3 Sepolia (not mainnet, not other testnets).

## Known failure modes

- Invalid JSON-RPC method name returns error code -32601 method not found
- Malformed params array returns error code -32602 invalid params
- Network unavailable or node down returns HTTP 503 or JSON-RPC internal error -32603
- Insufficient payment (x402 payment missing or wrong amount) returns HTTP 402 Payment Required
- Unsupported method for B3 Sepolia returns error response
- Transaction submission with bad nonce or gas returns execution error

## How this service works

JSON-RPC proxy — b3-sepolia

## Output

Returns a standard JSON-RPC 2.0 response object containing the result of the requested blockchain method — e.g. block number as a hex string, account balance in wei, transaction receipt object, or contract call return data — along with the matching request id and jsonrpc version field.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "jsonrpc",
  "method"
 ],
 "properties": {
  "id": {
   "type": [
    "number",
    "string"
   ],
   "description": "Request identifier"
  },
  "method": {
   "type": "string",
   "description": "JSON-RPC method name (e.g., eth_blockNumber, eth_call)"
  },
  "params": {
   "type": "array",
   "description": "Method parameters"
  },
  "jsonrpc": {
   "type": "string",
   "const": "2.0"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "id": {
   "type": [
    "number",
    "string"
   ]
  },
  "error": {
   "type": "object",
   "properties": {
    "code": {
     "type": "integer"
    },
    "message": {
     "type": "string"
    }
   }
  },
  "result": {
   "description": "RPC result (type varies by method)"
  },
  "jsonrpc": {
   "type": "string",
   "const": "2.0"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/quicknode-7cd3a0cf/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.quicknode.com](https://www.zero.xyz/host/x402.quicknode.com/llms.txt)