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Fact Check
aifact-checkverifyllmaccuracy
Fact Check is a paid API for AI agents from ZeroClick x402 Service Registry at factcheck.withzero.ai, paid per call via MPP, $0.005/call, status unknown (last checked 2026-10-11).
Verify a factual claim using a second AI model via OpenRouter, returning a structured verdict (true/false/uncertain) with confidence score, reasoning, and corrections.
Price / call$0.005
Success—
StatusUnknown
How this service works
Verify factual claims using a second AI model via OpenRouter. Submit a claim and optionally provide context — returns a structured verdict (true/false/uncertain) with confidence score, reasoning, and corrections if the claim is false. Useful for cross-referencing your primary model's outputs against a different model. Default model: Gemini 2.5 Flash (fast and cheap). Use a stronger model for complex claims.
Output
Returns a structured object with the original claim, the verdict (true/false/uncertain), a confidence score from 0–100, a brief reasoning explanation, corrections if the claim is false (null otherwise), the model used, and response latency in milliseconds.
Example use cases
Example prompt
“Can you fact-check this claim for me — 'The Eiffel Tower is 330 meters tall' — and tell me if it's true or false, how confident you are, and what the correct figure is if it's wrong? Use GPT-4.1-mini for this one.”
Technical details
Endpoint
POSThttps://factcheck.withzero.ai/run?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to cross-validate AI-generated content or user-supplied claims against a second independent model without building your own fact-checking pipeline. Especially useful when your primary model might hallucinate and you want a cheap, structured verdict with reasoning. Prefer a stronger model (e.g. GPT-4.1-mini or DeepSeek V3) for nuanced or complex claims; use the default Gemini 2.5 Flash for speed and cost efficiency.
Side effects
- Claim text is empty or missing — returns 400 validation error
- Claim or context exceeds 5000 characters — returns 400 error
- Invalid model name specified — may fallback or return 400
- Upstream OpenRouter/model timeout — returns 5xx error
- Ambiguous claim with low-confidence result — verdict may be 'uncertain' with low confidence score
Input
{
"claim": "Water boils at 100 degrees Celsius at sea level"
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| claimrequired | string | The factual claim to verify (e.g. "The Eiffel Tower is 330 meters tall") |
| model | string | Model to use for fact-checking (default: google/gemini-2.5-flash). Available: openai/gpt-4.1-mini, google/gemini-2.5-flash, meta-llama/llama-3.3-70b-instruct, deepseek/deepseek-v3, mistralai/mistral-small |
| context | string | Optional context or source material the claim is derived from |
Output
{
"claim": "Water boils at 100 degrees Celsius at sea level",
"model": "google/gemini-2.5-flash",
"verdict": "true",
"latencyMs": 775,
"reasoning": "The boiling point of water at standard atmospheric pressure (which is approximately at sea level) is indeed 100 degrees Celsius (212 degrees Fahrenheit). This is a fundamental scientific constant.",
"confidence": 100,
"corrections": null
}Schema · Response
| Field | Type | Description |
|---|---|---|
| claimrequired | string | The original claim that was checked |
| modelrequired | string | Model used for fact-checking |
| verdictrequired | string | Fact-check verdict |
| latencyMsrequired | number | Response time in milliseconds |
| reasoningrequired | string | Brief explanation of the verdict |
| confidencerequired | number | Confidence level 0-100 |
| correctionsrequired | string | Correct information if claim is false, null otherwise |
Tags
aifact-checkverifyllmaccuracy
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