AI Inference · x402 · early usage

PRESENCE tier (deterministic, no LLM): confirms the claimed value appears on the live p…

by scrapecheck.fly.dev · discovered, not yet claimed by its owner · updated 2026-10-11

30d calls2

30d payers2

MethodPOST

Outputjson

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

PRESENCE tier (deterministic, no LLM): confirms the claimed value appears on the live page — it does NOT confirm the value is the right answer to the question. Positive verdict is "present", never "pass"; check_type web_field_presence_v1. For full verification use /verify. First 100 checks per client are free: resend with header X-Use-Free-Allowance: yes and no payment to use them.

Tags: verification · scraping · data-quality · presence · bazaar · errorNote · errors

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-11

Input example from Bazaar metadata

{
  "asked": "get the current price and stock status of A Light in the Attic",
  "claim": {
    "in_stock": true,
    "price": "£51.77"
  },
  "url": "https://books.toscrape.com/catalogue/a-light-in-the-attic_1000/index.html"
}

Output example

{
  "check_type": "web_field_presence_v1",
  "confidence": 0.9,
  "engine": "web_field_v1/0.2.1+6739b7f9ebf8",
  "evidence": {
    "lens_votes": {
      "is_current": true,
      "is_real": true
    },
    "refetch_excerpt": "…£51.77 In stock…",
    "refetched_at": "2026-08-15T01:50:06.202Z"
  },
  "key_id": "k2",
  "reasons": [
    "claimed price £51.77 found in re-fetched page",
    "presence check only: confirms the value appears on the live page — not that it answers the question"
  ],
  "signature": "ed25519:…",
  "source_hash": "sha256:…",
  "verdict": "present",
  "verdict_id": "0d2c…",
  "verifier_url": "https://scrapecheck.fly.dev"
}

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/38724.json for the price and payment options.
Pay. Call GET https://scrapecheck.fly.dev/verify-presence. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, Polygon, Solana, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.002 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base, Polygon, Solana
Demand: 2 calls · 2 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.002	0x455F20eC147477CAFcd6D77C1604529f3c4Ff665	300s
exact	Polygon eip155:137	USDC	$0.002	0x455F20eC147477CAFcd6D77C1604529f3c4Ff665	300s
exact	Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp	USDC	$0.002	4HuSbgqgKkeUM5jEzAzLGpxtivCGda9eEtYc2Sp1fLpM	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x455F20eC147477CAFcd6D77C1604529f3c4Ff665",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "eip155:137",
    "payTo": "0x455F20eC147477CAFcd6D77C1604529f3c4Ff665",
    "asset": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "4HuSbgqgKkeUM5jEzAzLGpxtivCGda9eEtYc2Sp1fLpM",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "properties": {
        "check_type": {
          "description": "The check contract used, e.g. web_field_presence_v1.",
          "type": "string"
        },
        "confidence": {
          "description": "The engine's confidence in the verdict, 0 to 1.",
          "type": "number"
        },
        "engine": {
          "description": "Engine name and version digest that produced the verdict.",
          "type": "string"
        },
        "evidence": {
          "description": "What the re-fetch observed.",
          "properties": {
            "lens_votes": {
              "description": "Boolean votes is_real, is_current from the judging lenses.",
              "properties": {
                "is_current": {
                  "type": "boolean"
                },
                "is_real": {
                  "type": "boolean"
                }
              },
              "type": "object"
            },
            "refetch_excerpt": {
              "description": "Excerpt of the re-fetched page content the verdict was judged against.",
              "type": "string"
            },
            "refetched_at": {
              "description": "UTC timestamp of the engine's own fetch of the page.",
              "type": "string"
            }
          },
          "type": "object"
        },
        "key_id": {
          "description": "Identifier of the signing key; resolve against GET /pubkey.",
          "type": "string"
        },
        "reasons": {
          "description": "The stated reasons for the verdict.",
          "items": {
            "type": "string"
          },
          "type": "array"
        },
        "signature": {
          "description": "ed25519 signature over canonical sorted-key JSON of every field except signature.",
          "type": "string"
        },
        "source_hash": {
          "description": "sha256 of the normalized page text the verdict judged; null when no anchor text was obtained.",
          "type": [
            "string",
            "null"
          ]
        },
        "verdict": {
          "description": "One of present, fail, unverifiable.",
          "enum": [
            "present",
            "fail",
            "unverifiable"
          ],
          "type": "string"
        },
        "verdict_id": {
          "description": "Unique identifier for this verdict; its issuance is confirmable at GET /verdicts/{verdict_id}.",
          "type": "string"
        },
        "verifier_url": {
          "description": "The issuing service's URL; display only, never a trust root.",
          "type": "string"
        }
      },
      "required": [
        "verdict_id",
        "verdict",
        "confidence",
        "reasons",
        "evidence",
        "check_type",
        "engine",
        "key_id",
        "verifier_url",
        "source_hash",
        "signature"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

Example shape — generated from the schema, not a captured live response

{
  "example": {
    "check_type": "string",
    "confidence": 0,
    "engine": "string",
    "evidence": {
      "lens_votes": {
        "is_current": true,
        "is_real": true
      },
      "refetch_excerpt": "string",
      "refetched_at": "string"
    },
    "key_id": "string",
    "reasons": [
      "string"
    ],
    "signature": "string",
    "source_hash": "string",
    "verdict": "present",
    "verdict_id": "string",
    "verifier_url": "string"
  },
  "type": "string"
}

Examples

curl

curl -X POST 'https://scrapecheck.fly.dev/verify-presence' -H 'Content-Type: application/json' --data '{"asked":"get the current price and stock status of A Light in the Attic","claim":{"in_stock":true,"price":"£51.77"},"url":"https://books.toscrape.com/catalogue/a-light-in-the-attic_1000/index.html"}'
# -> 402 Payment Required; read PAYMENT-REQUIRED
# retry the identical request with PAYMENT-SIGNATURE

JavaScript

const res = await fetch("https://scrapecheck.fly.dev/verify-presence", {
  "method": "POST",
  "headers": {
    "content-type": "application/json"
  },
  "body": "{\"asked\":\"get the current price and stock status of A Light in the Attic\",\"claim\":{\"in_stock\":true,\"price\":\"£51.77\"},\"url\":\"https://books.toscrape.com/catalogue/a-light-in-the-attic_1000/index.html\"}"
});
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
import json
res = httpx.request("POST", "https://scrapecheck.fly.dev/verify-presence", json=json.loads("{\"asked\":\"get the current price and stock status of A Light in the Attic\",\"claim\":{\"in_stock\":true,\"price\":\"£51.77\"},\"url\":\"https://books.toscrape.com/catalogue/a-light-in-the-attic_1000/index.html\"}"))
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: scrapecheck.fly.dev
Endpoint: https://scrapecheck.fly.dev/verify-presence
Machine-readable: /resources/38724.json