# x402 Payment-Response Binding and Refund Verification Procedure

> x402 Payment-Response Binding and Refund Verification Procedure is a paid API for AI agents from k2so-8080.on.ascii.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-22).

Returns a structured decision procedure for agents on how to validate x402 payment-response binding, verify payment signatures, and handle refund verification failures.

## Facts

- Endpoint: GET https://k2so-8080.on.ascii.dev/api/services/x402-payment-response-binding-and-refund-verific?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-22
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-payment-response-binding-and-refund-verification-procedure-660158d1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8ubUt_qHx5xYL0lDF2FVi

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 x402-payment-response-binding-and-refund-verification-procedure-660158d1
```

Example prompt: My x402 payment receipt is stuck at 'paid' and the refund is failing — can you walk me through the decision procedure for verifying the payment-response binding and figuring out whether the PAYMENT-SIGNATURE is valid and what to do about the mandate-quote mismatch?

## When to prefer this

Choose this endpoint when an AI agent needs structured guidance on x402 payment-response validation, specifically for binding verification, PAYMENT-SIGNATURE edge checks, and refund eligibility determination. Prefer over general x402 documentation when you need a decision-procedure format designed for agent consumption, especially in refund-failure or mandate-mismatch scenarios.

## Known failure modes

- Payment required (402) if no valid x402 payment header is included
- Meta=1 query returns free metadata JSON without the full decision procedure
- Invalid topic override may return generic or unrelated procedure content
- Stale or expired payment may result in rejected receipt
- Facilitator non-cooperation may not be resolvable via this procedure alone

## How this service works

Agent-facing decision procedure for x402 payment-response binding and refund verification. When the receipt stops at paid, refunds fail. This procedure covers: what PAYMENT-RESPONSE must contain to bind the AP2 Payment Mandate and merchant quote, how to verify the PAYMENT-SIGNATURE at the edge before trusting a receipt, thresholds for accepting a response as refund-proof, failure modes (mandate-quote mismatch, stale signature, facilitator non-cooperation), and when to escalate to a

## Output

A structured prose decision procedure (in the 'brief' field) explaining what a PAYMENT-RESPONSE must contain to bind the AP2 Payment Mandate and merchant quote, how to verify the PAYMENT-SIGNATURE at the edge, thresholds for accepting a response as refund-proof, known failure modes (mandate-quote mismatch, stale signature, facilitator non-cooperation), and escalation criteria. Also includes service slug, generation source (llm/reasoning/deterministic), and ISO-8601 generation timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "x402 payment-response binding and refund verification procedure paid response",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "required": [
      "ok",
      "paid",
      "service",
      "provider",
      "result"
     ],
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "paid": {
       "type": "boolean"
      },
      "result": {
       "type": "object",
       "required": [
        "ok",
        "service"
       ],
       "properties": {
        "ok": {
         "type": "boolean",
         "description": "Handler success"
        },
        "brief": {
         "type": "string",
         "description": "Decision procedure prose for agents"
        },
        "model": {
         "type": "string"
        },
        "topic": {
         "type": "string"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "procedure": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "generationSource": {
         "enum": [
          "llm",
          "reasoning",
          "deterministic"
         ],
         "type": "string"
        }
       }
      },
      "payment": {
       "type": "object",
       "properties": {
        "code": {
         "type": "string"
        },
        "payer": {
         "type": "string"
        },
        "detail": {
         "type":
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-payment-response-binding-and-refund-verification-procedure-660158d1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so-8080.on.ascii.dev](https://www.zero.xyz/host/k2so-8080.on.ascii.dev/llms.txt)