# Base Payment Proof Verifier

> Base Payment Proof Verifier is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-15).

Verifies and risk-assesses a Base blockchain USDC payment transaction by checking its hash, recipient, and amount on-chain.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/base/payment-proof
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-payment-proof-verifier-cddae9ee
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_9ExN4tI_JOIXG653YZKqr

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-payment-proof-verifier-cddae9ee
```

Example prompt: Can you verify that Base transaction 0x3a7f...c9d2 actually sent 5.00 USDC to 0xAbCd...1234 and tell me the risk score before I release the download?

## When to prefer this

Use this endpoint when an AI agent needs to confirm that a specific Base blockchain USDC payment was executed with the correct amount and recipient before fulfilling an obligation, releasing goods, or logging compliance. Prefer this over generic blockchain explorers when you need a structured, machine-readable risk assessment with flags rather than raw on-chain data.

## Known failure modes

- Invalid transaction hash format (not 0x + 64 hex chars) returns validation error
- Transaction not found on Base network returns not-found error
- Amount or recipient mismatch between on-chain data and query params may raise risk flags
- Network timeout or Base RPC unavailability may return 5xx error
- Missing required query params (tx, recipient, amount) returns 400 error

## How this service works

Verifies a Base transaction against an expected USDC payment recipient and amount, and returns proof details including transfer match and finality metadata.

## Output

Returns a JSON object with network identifier (eip155:8453), product label (base-payment-proof), a risk assessment containing a risk_score (numeric), risk_level (e.g. 'low'), and any risk flags, plus activity, identity, and provenance metadata about the transaction.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "tx",
      "recipient",
      "amount"
     ],
     "properties": {
      "tx": {
       "type": "string",
       "pattern": "^0x[a-fA-F0-9]{64}$",
       "description": "Base transaction hash."
      },
      "amount": {
       "type": "string",
       "pattern": "^[0-9]+(?:\\.[0-9]{1,6})?$",
       "description": "Expected USDC amount in decimal units."
      },
      "recipient": {
       "type": "string",
       "pattern": "^0x[a-fA-F0-9]{40}$",
       "description": "Expected USDC recipient."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "network": {
       "type": "string"
      },
      "product": {
       "type": "string"
      },
      "activity": {
       "type": "object"
      },
      "identity": {
       "type": "object"
      },
      "assessment": {
       "type": "object"
      },
      "provenance": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "base-payment-proof",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-payment-proof-verifier-cddae9ee/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-agent-preflight.bytoken2023.workers.dev](https://www.zero.xyz/host/base-agent-preflight.bytoken2023.workers.dev/llms.txt)