# AgentIndex x402 Fact-Check

> AgentIndex x402 Fact-Check is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-13).

Verifies a factual claim against live web sources and returns a verdict with supporting evidence and confidence score

## Facts

- Endpoint: POST https://x402.agentindex.world/fact-check
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentindex-x402-fact-check-0190ddd2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_RWgQbhR_ZkQhPb3okyBOx

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 agentindex-x402-fact-check-0190ddd2 -d '<json body>'
```

Example prompt: Can you fact-check this claim for me: 'The Great Wall of China is visible from space' — I want to know if it's supported or refuted with real sources and how confident you are?

## When to prefer this

Choose this endpoint when you need a structured, sourced verdict on a specific factual claim backed by live web retrieval — especially when you need a machine-readable confidence score and stance-labeled citations. Prefer it over generic search when you need a binary or graded fact-check output rather than raw search results. Best suited for agents performing misinformation detection, research validation, or automated journalism workflows.

## Known failure modes

- Claim is ambiguous or too broad — may return low confidence or inconclusive verdict
- Live web sources unavailable or unreachable — may result in error or reduced source count
- Claim involves highly niche or recent events not yet indexed — may return inconclusive with few sources
- Malformed or empty claim field — returns validation error
- Payment failure via x402 protocol — returns 402 Payment Required

## How this service works

Read and search the web for AI agents. Nothing else. A pay-per-call kit for AI agents in USDC on Base (x402/MPP): search, pdf, web-read, extract, summarize, fact-check, and the free detect-language entry point - see GET /capabilities. Plus two tools outside the kit: translate and jobs.

## Output

A JSON object containing the original claim, a verdict ('supported', 'refuted', or 'inconclusive'), a confidence score between 0 and 1, and a list of sources each with a URL, title, and stance ('supports' or 'refutes') drawn from live web retrieval.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "claim": {
   "type": "string",
   "description": "The factual claim to check against live web sources."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "claim": "The Eiffel Tower is taller than the Statue of Liberty.",
  "sources": [
   {
    "url": "https://example.com/eiffel-tower-facts",
    "title": "Eiffel Tower Facts",
    "stance": "supports"
   }
  ],
  "verdict": "supported",
  "confidence": 0.92
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentindex-x402-fact-check-0190ddd2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.agentindex.world](https://www.zero.xyz/host/x402.agentindex.world/llms.txt)