AI Inference · x402 · early usage

Fact-check verdict written by Claude Haiku 5.5 (Anthropic) from real web sources: suppo…

Fact-check verdict written by Claude Haiku 5.5 (Anthropic) from real web sources: supported/contradicted/mixed/unverifiable, each source with its stance (supports/contradicts/neutral). Answer in a few seconds. Try GET /fact-check/sample.

by x402.agentindex.world · discovered, not yet claimed by its owner · updated 2026-10-12

30d calls4

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

Tags: fact check api · claim verification · claude · fact checking · sources · bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-12

Input example from Bazaar metadata

{
  "claim": "The Eiffel Tower is taller than the Statue of Liberty."
}

Output example

{
  "claim": "The Eiffel Tower is taller than the Statue of Liberty.",
  "confidence": 0.92,
  "sources": [
    {
      "stance": "supports",
      "title": "Eiffel Tower Facts",
      "url": "https://example.com/eiffel-tower-facts"
    }
  ],
  "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/33908.json for the price and payment options.
Pay. Call GET https://x402.agentindex.world/fact-check. 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: $0.02 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 4 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	$0.02	0xb3F32bdfe8D07825BC0D7387295aB1D7559BA69d	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xb3F32bdfe8D07825BC0D7387295aB1D7559BA69d",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "20000",
    "amountUsd": 0.02,
    "maxTimeoutSeconds": 300
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "properties": {
        "claim": {
          "type": "string"
        },
        "confidence": {
          "description": "0.0-1.0 confidence in the verdict.",
          "type": "number"
        },
        "sources": {
          "items": {
            "properties": {
              "stance": {
                "enum": [
                  "supports",
                  "contradicts",
                  "neutral"
                ],
                "type": "string"
              },
              "title": {
                "description": "Source page title, when known."
              },
              "url": {
                "type": "string"
              }
            },
            "type": "object"
          },
          "type": "array"
        },
        "verdict": {
          "description": "'inconclusive' is returned instead of a guess whenever confidence is low or no source clearly supports/contradicts the claim - never a confident-sounding verdict the sources don't actually back up.",
          "enum": [
            "supported",
            "contradicted",
            "mixed",
            "unverifiable",
            "inconclusive"
          ],
          "type": "string"
        },
        "x402_receipt": {
          "description": "Billing and provenance receipt for this call.",
          "type": "object"
        }
      },
      "required": [
        "claim",
        "verdict",
        "confidence",
        "sources"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

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

{
  "example": {
    "claim": "string",
    "confidence": 0,
    "sources": [
      {
        "stance": "supports",
        "title": null,
        "url": "string"
      }
    ],
    "verdict": "supported",
    "x402_receipt": {}
  },
  "type": "string"
}

Examples

curl

curl "https://x402.agentindex.world/fact-check"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://x402.agentindex.world/fact-check");
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://x402.agentindex.world/fact-check")
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: x402.agentindex.world
Endpoint: https://x402.agentindex.world/fact-check
Machine-readable: /resources/33908.json