# Quartermaster Payment Proof Verifier

> Quartermaster Payment Proof Verifier is a paid API for AI agents from quartermaster.surewhynot.app, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).

Verifies a Base blockchain transaction for x402 settlement: confirms success, decodes USDC transfers, and optionally asserts the recipient wallet and amount.

## Facts

- Endpoint: GET https://quartermaster.surewhynot.app/v1/payment-proof
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/quartermaster-payment-proof-verifier-8c8c4046
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jRWpacdJRfE03sKPjUKoO

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 quartermaster-payment-proof-verifier-8c8c4046
```

Example prompt: Can you verify that this Base transaction 0x3a7f1b2c... actually succeeded and that 0.50 USDC was received by wallet 0xABCD...1234?

## When to prefer this

Use this endpoint when you need to cryptographically confirm that an x402 USDC payment on Base was settled — especially when you want to assert a specific recipient wallet and/or amount. Prefer this over generic blockchain explorers when you need structured, machine-readable proof suitable for automated agent workflows.

## Known failure modes

- Invalid or malformed transaction hash (not matching ^0x[0-9a-fA-F]{64}$) returns a 400 error
- Transaction not found on Base returns a not-found or failed status
- Transaction found but USDC transfer does not match asserted payTo wallet or amount returns a mismatch error
- Transaction is still pending and not yet confirmed
- RPC or Base node connectivity issues causing lookup failure

## How this service works

Verify an x402 settlement on Base OR Solana: pass a 0x transaction hash or a base58 signature, confirm it succeeded, decode its USDC transfers (event logs on Base, net token-balance deltas on Solana), and optionally assert the receiving wallet and amount.

## Output

Returns confirmation of whether the Base transaction succeeded, decoded USDC transfer amounts, sender/recipient addresses, and optionally whether the asserted payTo wallet and amount match the on-chain data.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "hash"
     ],
     "properties": {
      "hash": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{64}$",
       "description": "Base transaction hash to verify"
      },
      "payTo": {
       "type": "string",
       "description": "Optional: assert USDC was received by this wallet"
      },
      "amount": {
       "type": "string",
       "description": "Optional: assert the USDC amount (human decimal)"
      }
     }
    }
   },
   "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/quartermaster-payment-proof-verifier-8c8c4046/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from quartermaster.surewhynot.app](https://www.zero.xyz/host/quartermaster.surewhynot.app/llms.txt)