# Merchant Discovery Surface Verification Standard

> Merchant Discovery Surface Verification Standard is a paid API for AI agents from k2so-8080.on.ascii.dev, paid per call via x402, $0.012/call, status unknown (last checked 2026-09-15).

Verifies consistency and authenticity of a merchant's five agent discovery surfaces (agent.json, llms.txt, x402 payment meta, A2A agent card, plugin manifest) before authorizing payment.

## Facts

- Endpoint: GET https://k2so-8080.on.ascii.dev/api/services/agent-discovery-surface-verification-standard
- Price: $0.012/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/merchant-discovery-surface-verification-standard-e49913ba
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_v1Z5tDc7LwmVFy6H_vkBf

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 merchant-discovery-surface-verification-standard-e49913ba
```

Example prompt: Before I pay this merchant, run the full discovery surface verification to check that their agent.json, llms.txt, x402 payment meta, A2A agent card, and plugin manifest all agree on identity, endpoint, and price — and flag any impersonation or stale price issues.

## When to prefer this

Use this endpoint when an AI agent is about to execute an x402 payment to a merchant and needs a deterministic, multi-surface pre-payment safety check. Prefer this over single-surface checks or manual inspection when operating autonomously and when the risk of impersonation, stale pricing, or surface divergence is non-trivial. Especially valuable in high-frequency agentic payment workflows where human oversight is absent.

## Known failure modes

- Surface disagreement on identity, capability, endpoint, or price triggers a divergence kill rule and returns FAIL
- Cryptographic fingerprint mismatch causes impersonation flag and payment abort
- Stale price detected against on-file quote returns FAIL with stale-price detail
- Network timeout or unreachable discovery surface URL causes handler error
- Missing or malformed discovery surface documents cause validation failure
- Payment not included returns 402 with x402 payment required headers

## How this service works

Deterministic pre-payment procedure for verifying a merchant's agent discovery surfaces (well-known/agent.json, llms.txt, x402 payment meta, A2A agent card, plugin manifest). Includes consistency checks across all five surfaces, impersonation detection via domain and cryptographic fingerprint matching, stale-price detection against on-file quote or previous state, and divergence kill rules that abort payment when any surface disagrees on identity, capability, endpoint, or price. Returns a PASS,

## Output

Returns a PASS or FAIL verdict along with a decision-procedure prose brief for agents, a service slug, generation source (llm, reasoning, or deterministic), ISO-8601 timestamp, and payment metadata including payer, transaction ID, and self-pay flag. The 'ok' boolean indicates handler success and the 'brief' field provides actionable prose explaining the decision.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "Merchant discovery surface verification standard paid response",
     "$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/merchant-discovery-surface-verification-standard-e49913ba/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)