# code402 Ethereum Address Nonce Lookup

> code402 Ethereum Address Nonce Lookup is a paid API for AI agents from verify.code402.dev, paid per call via x402, $0.5/call, status unknown (last checked 2026-09-30).

Fetches the current transaction nonce for a given Ethereum address via the code402 chain-data API, paid per call via x402 on Base USDC.

## Facts

- Endpoint: GET https://verify.code402.dev/v1/chain/nonce/%7Baddress%7D?utm_source=zero.xyz
- Price: $0.5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/code402-ethereum-address-nonce-lookup-3d512c0f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_crCPXLf_BzI_pG7jNtAP1

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 code402-ethereum-address-nonce-lookup-3d512c0f
```

Example prompt: What's the current transaction nonce for the Ethereum address 0xAbC123...456 — I need it before signing my next transaction?

## When to prefer this

Choose this endpoint when you need a quick, pay-per-call lookup of an Ethereum address's current nonce without setting up your own node or RPC infrastructure. It is especially useful for agents that occasionally need on-chain sequence data without maintaining persistent blockchain connections, and where the x402 micropayment model on Base USDC is acceptable.

## Known failure modes

- Invalid or malformed Ethereum address returns an error response
- Payment not fulfilled via x402 results in HTTP 402 Payment Required
- Network unavailability or node errors may return 500-level responses
- Address with no on-chain history may return nonce of 0, which is valid but could be misinterpreted

## How this service works

Deterministic compliance verification (IBAN, sanctions, onchain address) with XDR-1 signed receipts, plus Ethereum chain-data endpoints. Paid per call via x402 on Base (USDC).

## Output

Returns a JSON object containing the current transaction nonce for the queried Ethereum address, along with the network name (e.g. 'ethereum') and a result field confirming the chain data. This allows callers to determine the next valid transaction sequence number for the address.

## Request schema (JSON Schema)

```json
{
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "type": "string",
     "enum": [
      "GET"
     ]
    },
    "queryParams": {
     "type": "object"
    }
   },
   "required": [
    "type",
    "method"
   ]
  },
  "output": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string",
     "const": "json"
    },
    "example": {
     "result": "string",
     "network": "ethereum-mainnet"
    }
   },
   "required": [
    "type",
    "example"
   ]
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": "chain data",
  "network": "ethereum"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/code402-ethereum-address-nonce-lookup-3d512c0f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from verify.code402.dev](https://www.zero.xyz/host/verify.code402.dev/llms.txt)