# Verifypost — Base Address Verification

> Verifypost — Base Address Verification is a paid API for AI agents from oraclepost.higgsfield.app, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-19).

Checks whether a Base blockchain address is a contract or EOA wallet, and returns its activity status (code size, nonce, ETH balance, USDC balance) at the latest block.

## Facts

- Endpoint: GET https://oraclepost.higgsfield.app/api/premium/verify
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/verifypost-base-address-verification-90b80de8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_lLhyaBxoaoeKCEnfH9Rml

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 verifypost-base-address-verification-90b80de8
```

Example prompt: Before I send payment, can you verify whether 0x1234567890abcdef1234567890abcdef12345678 is a contract or a regular wallet on Base, and tell me if it's active — show me its ETH and USDC balance and transaction count?

## When to prefer this

Choose this endpoint when you need to perform pre-payment due diligence on an unknown Base address — it uniquely combines contract-vs-EOA classification, activity check (nonce), and balance snapshot in a single live read with no third-party APIs or caching. Prefer it over wallet-only balance endpoints when you also need to know whether the recipient is a smart contract.

## Known failure modes

- Invalid or malformed address (not 0x-prefixed or wrong length) returns an error
- Address with zero nonce and zero balances may appear inactive even if valid
- RPC node unavailability could cause transient read failures
- Non-Base EVM addresses (e.g. Ethereum mainnet) may return misleading results if the address exists on both chains

## How this service works

Is this Base address a contract or a wallet, and is it active? Live read: code size (contract vs EOA), transaction count (nonce), ETH and USDC balance, at the latest block. Pass ?address=0x... . Useful before paying an unknown payTo. No third-party API, no cache.

## Output

Returns the account type (contract if code size > 0, EOA otherwise), the raw code size in bytes, the nonce (total transaction count), the current ETH balance, and the current USDC balance — all read live from the Base chain at the latest block with no caching.

## 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": {
     "const": "http"
    },
    "method": {
     "const": "GET"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "address": {
       "type": "string",
       "description": "EVM address on Base, 0x-prefixed"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {}
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/verifypost-base-address-verification-90b80de8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from oraclepost.higgsfield.app](https://www.zero.xyz/host/oraclepost.higgsfield.app/llms.txt)