Utilities · x402 · early usage

Verify whether a supplied public source page currently supports one atomic factual claim

Verify whether a supplied public source page currently supports one atomic factual claim. Returns supported, contradicted, or insufficient-evidence plus source snippets, or explicit blocked/unreachable/unsupported states. Not a general fact checker or web sea…

by source-claim-proof.mattskowronis.workers.dev · discovered, not yet claimed by its owner · updated 2026-10-08

30d calls3

30d payers3

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

Tags: bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-08

Input example from Bazaar metadata

{
  "claim": "The event begins at 7:00 PM.",
  "url": "https://example.com/event"
}

Output example

{
  "claim": "The event begins at 7:00 PM.",
  "content_hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
  "evidence": [
    {
      "evidence_type": "visible_text",
      "location": "Schedule",
      "polarity": "supports",
      "text": "Doors 6:30 PM. Program begins at 7:00 PM."
    }
  ],
  "final_url": "https://example.com/event",
  "reasoning_summary": "Visible schedule text states the program begins at 7:00 PM.",
  "retrieval_method": "direct_http",
  "retrieved_at": "2026-08-18T22:00:00.000Z",
  "service_version": "1.0.0",
  "source_status": "verified",
  "source_url": "https://example.com/event",
  "verdict": "supported"
}

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/40895.json for the price and payment options.
Pay. Call GET https://source-claim-proof.mattskowronis.workers.dev/v1/verify. 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, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.01 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 3 calls · 3 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.01	0x22B3D4485C8Dcd8FC4840a7570664747c9055530	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x22B3D4485C8Dcd8FC4840a7570664747c9055530",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 300
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "additionalProperties": false,
      "properties": {
        "claim": {
          "description": "The claim that was checked.",
          "type": "string"
        },
        "content_hash": {
          "description": "Hash of retrieved source content.",
          "type": "string"
        },
        "evidence": {
          "description": "Compact source snippets used for the verdict.",
          "items": {
            "additionalProperties": false,
            "properties": {
              "evidence_type": {
                "description": "Where the snippet came from on the source page.",
                "enum": [
                  "visible_text",
                  "heading",
                  "json_ld",
                  "meta",
                  "status"
                ],
                "type": "string"
              },
              "location": {
                "description": "Page location of the snippet, or null if unknown.",
                "type": [
                  "string",
                  "null"
                ]
              },
              "polarity": {
                "description": "Whether the snippet supports, contradicts, or is neutral.",
                "enum": [
                  "supports",
                  "contradicts",
                  "neutral"
                ],
                "type": "string"
              },
              "text": {
                "description": "Source snippet that supports or contradicts the claim.",
                "maxLength": 240,
                "type": "string"
              }
            },
            "required": [
              "text",
              "location",
              "evidence_type",
              "polarity"
            ],
            "type": "object"
          },
          "maxItems": 3,
          "type": "array"
        },
        "final_url": {
          "description": "Final URL after redirects.",
          "type": "string"
        },
        "reasoning_summary": {
          "description": "Short machine-readable reason for the verdict.",
          "maxLength": 400,
          "type": "string"
        },
        "retrieval_method": {
          "description": "How the source page was fetched.",
          "enum": [
            "direct_http",
            "browser_run",
            "official_api",
            "unsupported"
          ],
          "type": "string"
        },
        "retrieved_at": {
          "description": "UTC timestamp of the check.",
          "type": "string"
        },
        "service_version": {
          "description": "Source Claim Proof service version.",
          "type": "string"
        },
        "source_status": {
          "description": "verified, blocked, unreachable, unsupported, or insufficient_evidence.",
          "enum": [
            "verified",
            "blocked",
            "unreachable",
            "unsupported",
            "insufficient_evidence"
          ],
          "type": "string"
        },
        "source_url": {
          "description": "Requested source URL.",
          "type": "string"
        },
        "verdict": {
          "description": "supported, contradicted, or insufficient_evidence.",
          "enum": [
            "supported",
            "contradicted",
            "insufficient_evidence"
          ],
          "type": "string"
        }
      },
      "required": [
        "verdict",
        "claim",
        "source_url",
        "final_url",
        "source_status",
        "evidence",
        "reasoning_summary",
        "retrieval_method",
        "retrieved_at",
        "content_hash",
        "service_version"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

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

{
  "example": {
    "claim": "string",
    "content_hash": "string",
    "evidence": [
      {
        "evidence_type": "visible_text",
        "location": "string",
        "polarity": "supports",
        "text": "string"
      }
    ],
    "final_url": "string",
    "reasoning_summary": "string",
    "retrieval_method": "direct_http",
    "retrieved_at": "string",
    "service_version": "string",
    "source_status": "verified",
    "source_url": "string",
    "verdict": "supported"
  },
  "type": "string"
}

Examples

curl

curl "https://source-claim-proof.mattskowronis.workers.dev/v1/verify"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://source-claim-proof.mattskowronis.workers.dev/v1/verify");
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
res = httpx.get("https://source-claim-proof.mattskowronis.workers.dev/v1/verify")
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: source-claim-proof.mattskowronis.workers.dev
Endpoint: https://source-claim-proof.mattskowronis.workers.dev/v1/verify
Machine-readable: /resources/40895.json