# Paid LLM Receipt Delivery-Proof Verification Procedure

> Paid LLM Receipt Delivery-Proof Verification Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-30).

Returns a deterministic decision procedure for verifying that a paid LLM API call receipt proves actual delivery before consuming the output.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/per-model-run-receipt-verification-for-paid-llm?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/paid-llm-receipt-delivery-proof-verification-procedure-94c6532e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_mxZcD5BIRHITX8loTgGeV

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 paid-llm-receipt-delivery-proof-verification-procedure-94c6532e
```

Example prompt: After I paid for that LLM API call, walk me through the deterministic steps to verify the receipt actually proves delivery — checking the request hash binding, model run ID, output hash, and paid amount — before I use the response.

## When to prefer this

Use this endpoint when an agent has just completed a paid x402 LLM API call and needs a deterministic, step-by-step procedure to verify the receipt proves delivery before consuming or acting on the output. Prefer this over general payment validation tools when the specific concern is LLM output delivery proof, receipt hash binding, and refund/dispute classification in a per-model-run billing context.

## Known failure modes

- Receipt fields missing or malformed — procedure may flag unverifiable state
- Network timeout fetching the procedure — agent should retry per returned retry rules
- Payment not confirmed on-chain — endpoint returns unpaid/402 response
- Topic override not recognized — falls back to default per-model-run procedure
- LLM generation failure — generationSource field indicates fallback to deterministic output

## How this service works

Deterministic procedure an agent runs after paying for an LLM API call, before consuming output. Checks: receipt binds the request hash, names a model run id, captures the output hash before the output is used, matches the paid amount to the quoted price, sets timeout and retry gates for slow or missing responses, and classifies refund or dispute state when the run fails. Verdicts: delivery-proven, verify-more, refuse-output-with-evidence.

## Output

A structured brief containing a blunt, deterministic decision procedure in prose form, covering: request hash binding verification, model run ID validation, output hash capture before use, paid amount matching, timeout and retry rules, and refund-or-dispute state classification. Also includes metadata like generation timestamp, source, and service slug.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "Paid LLM receipt delivery-proof verification procedure paid response",
     "$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": "string"
… (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": "per-model-run-receipt-verification-for-paid-llm",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "per-model-run-receipt-verification-for-paid-llm",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/paid-llm-receipt-delivery-proof-verification-procedure-94c6532e/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)