# Script Master Labs x402 Fact Check API

> Script Master Labs x402 Fact Check API is a paid API for AI agents from mcp-x402.onrender.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Verifies a factual claim against U.S. federal data sources, returning a fact-check result, with payment settled in USDC on Base via x402.

## Facts

- Endpoint: GET https://mcp-x402.onrender.com/x402/fact-check
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/script-master-labs-x402-fact-check-api-e50e83c4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BTzKGy8jRo6yXcLW7Ziyw

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 script-master-labs-x402-fact-check-api-e50e83c4
```

Example prompt: Can you fact-check this claim for me using U.S. federal data: 'The U.S. unemployment rate dropped below 4% in 2023' — check it in the economics domain.

## When to prefer this

Use this endpoint when you need to verify a specific factual claim against authoritative U.S. government data sources and are willing to pay $0.15 USDC per check. Ideal for agents working in journalism, policy research, education, or compliance that need a quick, authoritative verdict on U.S.-federal-scope claims. Prefer this over general web search when you want structured fact-check output grounded in official federal data rather than scraped opinion or news articles.

## Known failure modes

- Missing required 'claim' parameter returns a 400 or validation error
- Claim is too vague or ambiguous for federal data to resolve — may return inconclusive result
- Payment not authorized or x402 header missing — returns 402 Payment Required
- Domain value not recognized — may fall back to general lookup or return an error
- Federal data source for the specific domain is unavailable — may return partial or no result
- Server timeout on Render free-tier infrastructure — may return 503 or hang

## How this service works

Pay-per-call crypto, RWA, federal, SEC, Section 8/HUD housing, and compliance APIs via x402. Primary: USDC on Base (eip155:8453). Also accepts Global Dollar (USDG) on Robinhood Chain (eip155:4663) via sovereign X-PAYMENT-TX. Hyphen routes only (e.g. /x402/gas-tracker, /x402/pha-lookup, /x402/sec-8k). MARKETPLACE REVIEW: use free /x402/playground/* (no key, no payment). Production /x402/* returns 402 unless paid via x402 or X-Api-Market-Key / X-API-Key from seller dashboard.

## Output

A fact-check assessment indicating whether the submitted claim is supported, contradicted, or unverifiable based on U.S. federal data, likely including a verdict, confidence level, and relevant sourcing or context from official government datasets. Payment of $0.15 USDC is charged per call via x402 on Base.

## 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": {
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "claim"
     ],
     "properties": {
      "claim": {
       "type": "string",
       "description": "The claim or statement to fact-check (required, max 300 chars)."
      },
      "domain": {
       "enum": [
        "grants",
        "contracts",
        "drug",
        "provider",
        "insider",
        "yields",
        "clinical",
        "general"
       ],
       "type": "string",
       "description": "Hint to route to the correct data source (optional — auto-detected)."
      }
     }
    }
   }
  },
  "output": {
   "properties": {
    "example": {}
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "example": {}
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/script-master-labs-x402-fact-check-api-e50e83c4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mcp-x402.onrender.com](https://www.zero.xyz/host/mcp-x402.onrender.com/llms.txt)