# Base Address Nonce Lookup

> Base Address Nonce Lookup is a paid API for AI agents from x402-data-api.sigrunner.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-20).

Returns the latest and pending transaction count (nonce) for a given Base mainnet address, useful for determining the next nonce before signing a transaction.

## Facts

- Endpoint: GET https://x402-data-api.sigrunner.workers.dev/chain/nonce?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-address-nonce-lookup-4b1a499f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gmcBjNlVBBQF17KghUAB2

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 base-address-nonce-lookup-4b1a499f
```

Example prompt: What's the current nonce for Base address 0x4200000000000000000000000000000000000006 — I need both the latest confirmed and pending values before I sign my next transaction.

## When to prefer this

Choose this endpoint when an AI agent or transaction-signing workflow needs to determine the correct nonce for a Base mainnet address before constructing or submitting a transaction. It is especially useful for avoiding nonce collisions or identifying stuck transactions by comparing latest vs. pending values. Prefer this over general-purpose Ethereum RPC calls when operating within the x402 micropayment ecosystem on Base.

## Known failure modes

- Missing or malformed address parameter returns an error
- Non-0x-prefixed or invalid address length causes a validation failure
- Address not found on Base mainnet may return nonce of 0
- Network or RPC issues may cause temporary unavailability
- Payment failure (x402) blocks access if USDC funds are insufficient

## How this service works

Transaction count (nonce) for a Base address, latest and pending. Use when an agent needs the next nonce for a Base address before signing a transaction.

## Output

A JSON object containing the Base chain identifier, the queried address, the latest confirmed nonce (number of mined transactions), and the pending nonce (including transactions in the mempool), e.g. {"chain":"base","address":"0x...","nonce_latest":1,"nonce_pending":1}.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "address": {
       "type": "string",
       "description": "0x-prefixed 20-byte Base address"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "address",
      "nonce_latest",
      "nonce_pending",
      "chain"
     ],
     "properties": {
      "chain": {
       "type": "string"
      },
      "address": {
       "type": "string"
      },
      "nonce_latest": {
       "type": "integer"
      },
      "nonce_pending": {
       "type": "integer"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "chain": "base",
  "address": "0x4200000000000000000000000000000000000006",
  "nonce_latest": 1,
  "nonce_pending": 1
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-address-nonce-lookup-4b1a499f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-data-api.sigrunner.workers.dev](https://www.zero.xyz/host/x402-data-api.sigrunner.workers.dev/llms.txt)