# x402index Verdict — API Listing Vetting & Demand Scoring

> x402index Verdict — API Listing Vetting & Demand Scoring is a paid API for AI agents from api.firstmention.uk, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-29).

Vets one or more x402-indexed API listings for demand, reliability, and seller credibility, returning a confidence-scored verdict and price-tier standing among peers.

## Facts

- Endpoint: GET https://api.firstmention.uk/s/x402index/verdict?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402index-verdict-api-listing-vetting-demand-scoring-e358fd88
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__HKg7bu8oPNRdOCRulrq3

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 x402index-verdict-api-listing-vetting-demand-scoring-e358fd88
```

Example prompt: Before I wire up this x402 API in my agent, can you vet the listing at https://api.example.com/s/websearch/search and tell me its demand tier, how many distinct payers it had in the last 30 days, and whether it's a proven seller or not?

## When to prefer this

Use this endpoint when an AI agent needs to programmatically vet or compare x402 pay-per-call API listings before committing to integration — especially when choosing between multiple candidates or verifying that a listing has real, sustained demand. Prefer this over manual inspection or generic API directories when operating within the x402/Base USDC payment ecosystem.

## Known failure modes

- Unknown or uncrawled listing URL returns low-confidence or null verdict
- Tag with no matching listings returns empty candidates
- limit out of range (must be 1–25) causes validation error
- resources array exceeding 25 items rejected
- Missing both resource and tag fields returns schema validation error

## How this service works

Pay-per-call HTTP APIs, paid with x402 in USDC on Base (eip155:8453): agentkit, api-change-check, basedue, basewatch, chainread, check-sanctions, chgwatch, company-facts, composite, edgar, feednews, pageaudit, solcheck, token-dd, txpreflight, walletcheck, webmd, webread, websearch, x402index. Each operation describes its service.

## Output

Returns a JSON object containing: a 'verdict' label (e.g. 'proven seller'), a 'demand' object with tier classification and 30-day distinct payer count, a 'confidence' rating (e.g. 'high'), and 'price_standing' showing how many tag peers exist and the listing's price percentile among them.

## 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"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "format": {
       "type": "string"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "signals": {
       "type": "object",
       "properties": {
        "listings": {
         "type": "number"
        },
        "saturated_tags": {
         "type": "array",
         "items": {
          "type": "string"
         }
        },
        "sellers_with_payers": {
         "type": "number"
        }
       }
      },
      "verdict": {
       "type": "string"
      },
      "generated_at": {
       "type": "string"
      },
      "recommendation": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "demand": {
   "tier": "high demand",
   "payers_30d": 2402
  },
  "verdict": "proven seller",
  "confidence": "high",
  "price_standing": {
   "tag_peers": 873,
   "percentile": 62
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402index-verdict-api-listing-vetting-demand-scoring-e358fd88/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.firstmention.uk](https://www.zero.xyz/host/api.firstmention.uk/llms.txt)