# x402 Payment-Response Binding and Refund Verification Decision Procedure

> x402 Payment-Response Binding and Refund Verification Decision Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status down (last checked 2026-10-03).

Returns a paid LLM-generated decision procedure brief explaining how to verify that an x402 payment response is correctly bound to a request and how to handle refund eligibility.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/x402-payment-response-binding-and-refund-verific?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: down
- Last checked: 2026-10-03
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-payment-response-binding-and-refund-verification-decision-360035b1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_D4jIArYxLo7V2lG1AWEbC

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-decision-360035b1
```

Example prompt: Give me the decision procedure for verifying that an x402 payment response is correctly bound to the original request and checking whether a refund is valid.

## When to prefer this

Choose this endpoint when an autonomous agent needs authoritative, prose-format guidance on x402 payment-response binding and refund verification — especially when building compliance logic, dispute resolution flows, or payment integrity checks into an agent. Prefer this over generic documentation when you need a machine-readable structured response with a timestamped, sourced procedure that an agent can act on directly.

## Known failure modes

- HTTP 402 returned if payment has not been settled — must pay exact USDC amount and retry with PAYMENT-SIGNATURE header
- Invalid or missing method enum value causes schema validation error
- Payment signature mismatch or replay attack detection causes rejection
- Service may return ok:false with error detail if LLM generation fails
- Stale or cached procedure may be returned depending on generation source

## 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 JSON object containing a plain-prose decision procedure (120+ words) generated by an LLM, covering how to bind an x402 payment response to its originating request and verify refund eligibility. Includes the model used, topic, service slug, ISO-8601 generation timestamp, and generation source (llm, reasoning, or deterministic). Also returns payment metadata including payer address and transaction hash.

## 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)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "paid": true,
  "result": {
   "ok": true,
   "brief": "plain prose decision procedure (120+ words)",
   "model": "deepseek/deepseek-v4-flash-0731",
   "topic": "string topic",
   "service": "x402-payment-response-binding-and-refund-verific",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "x402-payment-response-binding-and-refund-verific",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-payment-response-binding-and-refund-verification-decision-360035b1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so.wrong.systems](https://www.zero.xyz/host/k2so.wrong.systems/llms.txt)