# Base Payee Safety Check

> Base Payee Safety Check is a paid API for AI agents from base-token-check.fly.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-15).

Checks a Base blockchain address before an agent pays or approves it, reporting wallet/contract type, transaction history, contract age, and proxy status with allow/warn output.

## Facts

- Endpoint: GET https://base-token-check.fly.dev/v1/counterparty-check?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-payee-safety-check-6fc15f85
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_beJFla1W5t9ZiEp6CK-ZV

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-payee-safety-check-6fc15f85
```

Example prompt: Before I send payment to 0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD on Base, can you run a safety check on that address and tell me if it's a known wallet, whether it's ever sent transactions, and if it's a new or proxy contract?

## When to prefer this

Use this endpoint specifically when an AI agent or automated system is about to send funds or grant token approvals on the Base network and needs a pre-flight safety check on the recipient address. It is purpose-built for Base payee screening — prefer it over generic blockchain explorers when you need a structured allow/warn signal covering contract newness, proxy detection, and outgoing transaction history in a single call. Not a substitute for full contract audits or fraud proof.

## Known failure modes

- Invalid address format (not a 0x hex address of 40 characters) — schema validation error
- Address not found or unresolvable on Base — may return ambiguous wallet-like result
- Deleted/self-destructed contracts appear indistinguishable from wallets — false negative risk
- Proxy contracts flagged even if legitimate — possible false positive warns
- No wallet age data available — cannot assess how old a wallet is
- Network or RPC errors may cause lookup failure
- Rate limiting or payment failure ($0.01 USDC x402) blocks the call

## How this service works

Check a Base address before an agent pays or approves it. Input: one address. Output: allow or warn. Reports wallet or contract, whether the wallet has sent a transaction, whether a contract already had code 7 days ago, and whether it is a proxy (EIP-1967, EIP-1167, or implementation()). Warns on contract_is_new, proxy, or no_outgoing_transactions. Wallet age is unknown. A deleted contract looks like a wallet. Not proof of theft.

## Output

Returns an allow or warn verdict for the address, indicating whether it is a wallet or contract, whether the contract had code 7 days ago (new vs established), whether it has sent any outgoing transactions, and whether it is a proxy (EIP-1967, EIP-1167, or implementation() pattern). Warns if the contract is new, is a proxy, or has no outgoing transactions. Limitations: wallet age is unknown, deleted contracts appear as wallets, and a warn result is not proof of theft.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "address": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "Wallet or contract on Base to check before paying or approving it."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-payee-safety-check-6fc15f85/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-token-check.fly.dev](https://www.zero.xyz/host/base-token-check.fly.dev/llms.txt)