# Payment Verification Threshold and Billing Model Selector

> Payment Verification Threshold and Billing Model Selector 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 2026-10-16).

Returns a decision procedure and JSON schema for x402 merchants choosing among pay-per-verified-call, subscription credits, or hybrid billing models, including failed-attempt handling rules.

## Facts

- Endpoint: GET https://k2so-8080.on.ascii.dev/api/services/merchant-billing-model-selection-verified-call-c?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/payment-verification-threshold-and-billing-model-selector-c96337a0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_n1g6CAhIyQ1KKlrGknN6j

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 payment-verification-threshold-and-billing-model-selector-c96337a0
```

Example prompt: I'm setting up an x402 merchant endpoint and need to decide whether to use pay-per-verified-call, subscription credits, or a hybrid billing model — can you fetch the decision procedure and tell me which one fits a service where buyers need spend-limit validation and I want payment settled before serving the response?

## When to prefer this

Use this endpoint when you are an x402 merchant or developer building a paid API and need authoritative, schema-validated guidance on which billing model (pay-per-verified-call, subscription credits, or hybrid) best fits your payment and settlement requirements. Prefer this over generic documentation when you need machine-readable decision logic including failed-attempt handling and retry semantics integrated into an agent workflow.

## Known failure modes

- Authorization failure returns an error result with ok:false and no billing model selected
- Settlement rejection causes the procedure to return a failed-attempt rule set rather than a billing recommendation
- Timeout before response may result in incomplete output with partial procedure data
- Invalid or unsupported topic override causes the procedure to fall back to default decision logic
- Payment not received causes the endpoint to reject without serving the decision procedure

## How this service works

Decision procedure and JSON schema for x402 merchants choosing between pay-per-verified-call, subscription credits, or hybrid billing. Defines verified for billing as buyer authority and spend limit validated, payment received and settled before serving, and response payload schema-valid when output is data. Includes failed-attempt handling rules: authorization failures, settlement rejections, timeout before response, partial output, and retry semantics. Retries are billable only after a

## Output

Returns a JSON object with a decision procedure prose brief for agents, the selected billing model slug, a topic label, an ISO-8601 timestamp of generation, and the generation source (llm, reasoning, or deterministic), along with payment confirmation fields (ok, paid, provider, service).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "Payment verification threshold and billing selector paid response",
     "$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)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/payment-verification-threshold-and-billing-model-selector-c96337a0/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)