Fact Checker API
Fact-check claims by searching the web and returning relevant evidence snippets. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.
Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.
Quickstart -- MCP
Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):
{
"mcpServers": {
"fact-checker": {
"url": "https://fact-checker.api.klymax402.com/mcp"
}
}
}
Quickstart -- HTTP (x402)
curl -X POST "https://fact-checker.api.klymax402.com/api/check" \
-H "Content-Type: application/json" \
-d '{"claim":"..."}'
# -> 402 Payment Required, with an x402 payment challenge in the response body
Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.
Tools
| Tool | Method | Path | Price | Description |
|---|---|---|---|---|
research_check_fact | POST | /api/check | $0.012 | Fact-check a claim by searching for evidence online |
research_check_fact
Use this when you need to verify a factual claim, check if a statement is true, or find evidence supporting or contradicting a claim. Accepts a claim text and returns relevant web snippets, source URLs, and a confidence assessment. Do NOT use for general web scraping — use web_scrape_to_markdown instead. Do NOT use for SEO analysis — use seo_audit_page instead. Do NOT use for sentiment analysis — use sentiment_analyzer instead.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
claim | string | yes | The factual claim to verify (e.g., 'The Eiffel Tower is 330 meters tall') |
max_sources | number | no | Maximum number of sources to return (default: 5, max: 10) |
Example agent prompts
- "Verify a factual claim, check if a statement is true, or find evidence supporting or contradicting a claim"
Payment
- Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key
- Network: Base L2 (
eip155:8453) - Asset: USDC
- Facilitator: Coinbase CDP (primary), PayAI (fallback)
Part of klymax402
100 x402 micropayment APIs for AI agents -- one wallet, USDC on Base, zero signup.
- Catalog: https://klymax402.com/llms.txt
- Full API reference: https://klymax402.com/llms-full.txt
- Live stats: https://klymax402.com/stats
License
MIT