Fact-check AI answers with cited sources. Pay per call in USDC on Base via x402.
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Fact-check a whole answer: extracts every checkable claim and verifies each against Wikipedia, plus Wikidata structured facts for dates, numbers, quantities, ordinals and records. Returns per-claim verdict, confidence, quote, source URL, sentence span and suggested_correction (quoted only from cited sources when contradicted/outdated), plus an answer-level summary with overall_verdict, counts and problem_sentences. Abstained rather than guessed. Use to audit chatbot or RAG output. Price: $1.00 USDC on Base per call via x402; this MCP call returns payment instructions and POST /v1/check_answer returns the results. Read-only.
The full answer text to fact-check. Each factual sentence is checked separately.
Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type "caller". The response lists what was used in sources_used.
Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array.
Fact-check a whole answer: extracts every checkable claim and verifies each against Wikipedia, plus Wikidata structured facts for dates, numbers, quantities, ordinals and records. Returns per-claim verdict, confidence, quote, source URL, sentence span and suggested_correction (quoted only from cited sources when contradicted/outdated), plus an answer-level summary with overall_verdict, counts and problem_sentences. Abstained rather than guessed. Use to audit chatbot or RAG output. Price: $1.00 USDC on Base per call via x402; this MCP call returns payment instructions and POST /v1/check_answer returns the results. Read-only.
| Argument | Type | Description |
|---|---|---|
| answer* | string | The full answer text to fact-check. Each factual sentence is checked separately. |
| sources | array | Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type "caller". The response lists what was used in sources_used. |
| sources_only | boolean | Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array. |
{
"type": "object",
"required": [
"answer"
],
"properties": {
"answer": {
"type": "string",
"examples": [
"Marie Curie won two Nobel Prizes. She was born in Warsaw."
],
"minLength": 1,
"description": "The full answer text to fact-check. Each factual sentence is checked separately."
},
"sources": {
"type": "array",
"items": {
"type": "object",
"anyOf": [
{
"required": [
"url"
]
},
{
"required": [
"text"
]
}
],
"properties": {
"url": {
"type": "string",
"format": "uri",
"maxLength": 2048,
"description": "Public https URL. Fetched with a 3.5 s timeout and a 512 KB cap; http, file and other schemes, private / loopback / link-local / metadata addresses, IP-literal hosts, custom ports and URLs with credentials are rejected (HTTP 400, not charged). With text, it is only the citation link."
},
"text": {
"type": "string",
"maxLength": 20000,
"minLength": 1,
"description": "Source text to check the claim against (up to 20,000 characters). When given, no fetch is made."
},
"title": {
"type": "string",
"maxLength": 200,
"description": "Optional title shown in citations."
}
},
"description": "One source: {url} for a public https page we fetch, or {text, title?, url?} for text you already have.",
"additionalProperties": false
},
"maxItems": 10,
"description": "Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type \"caller\". The response lists what was used in sources_used."
},
"sources_only": {
"type": "boolean",
"default": false,
"description": "Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array."
}
},
"additionalProperties": false
}Use when a claim is high-stakes, or when check_answer or extract_claims marks it unsure (their next_step gives the exact request). Verifies up to three claims against Wikipedia, Wikidata, Google News, Europe PMC, FRED and SEC EDGAR; returns verdict, confidence, evidence for and against with URLs, and flags contradictions. Async: poll GET /v1/jobs/{job_id} free. $0.75 USDC on Base via x402. Read-only.
| Argument | Type | Description |
|---|---|---|
| answer* | string | The claim or short text to verify (up to three claims are checked). |
| sources | array | Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type "caller". The response lists what was used in sources_used. |
| sources_only | boolean | Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array. |
{
"type": "object",
"required": [
"answer"
],
"properties": {
"answer": {
"type": "string",
"examples": [
"US unemployment was 3.7% in December 2023."
],
"minLength": 1,
"description": "The claim or short text to verify (up to three claims are checked)."
},
"sources": {
"type": "array",
"items": {
"type": "object",
"anyOf": [
{
"required": [
"url"
]
},
{
"required": [
"text"
]
}
],
"properties": {
"url": {
"type": "string",
"format": "uri",
"maxLength": 2048,
"description": "Public https URL. Fetched with a 3.5 s timeout and a 512 KB cap; http, file and other schemes, private / loopback / link-local / metadata addresses, IP-literal hosts, custom ports and URLs with credentials are rejected (HTTP 400, not charged). With text, it is only the citation link."
},
"text": {
"type": "string",
"maxLength": 20000,
"minLength": 1,
"description": "Source text to check the claim against (up to 20,000 characters). When given, no fetch is made."
},
"title": {
"type": "string",
"maxLength": 200,
"description": "Optional title shown in citations."
}
},
"description": "One source: {url} for a public https page we fetch, or {text, title?, url?} for text you already have.",
"additionalProperties": false
},
"maxItems": 10,
"description": "Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type \"caller\". The response lists what was used in sources_used."
},
"sources_only": {
"type": "boolean",
"default": false,
"description": "Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array."
}
},
"additionalProperties": false
}Split a text (for example an AI-generated answer) into atomic factual claims. Each claim includes span, grounding_required, claim_type (number|date|quantity|quote|named_entity_fact|comparison|opinion|prediction|other), check_worthiness (high|medium|low), and the source sentence. Hedges are stripped, pronouns are resolved across sentences, and compound sentences are split. Questions, greetings, opinions and predictions are marked grounding_required false. Use before verify_claim. Price: $0.05 USDC on Base per call via x402; this MCP call returns payment instructions and POST /v1/extract_claims returns the claims. Read-only.
| Argument | Type | Description |
|---|---|---|
| text* | string | The text to split into claims, for example a chatbot answer. Up to a few thousand characters. |
{
"type": "object",
"required": [
"text"
],
"properties": {
"text": {
"type": "string",
"examples": [
"The Eiffel Tower is in Paris and was completed in 1889."
],
"minLength": 1,
"description": "The text to split into claims, for example a chatbot answer. Up to a few thousand characters."
}
},
"additionalProperties": false
}Check one factual claim against public Wikipedia sources and return a verdict (supported, contradicted, outdated, mixed or insufficient_evidence), a confidence score, a short reason, the supporting quote and the source URL. Says insufficient_evidence instead of guessing. Price: $1.00 USDC on Base per call via x402; this MCP call returns payment instructions and the paid HTTP route POST /v1/verify_claim returns the verdict. For a multi-source check use deep_verify. Read-only.
| Argument | Type | Description |
|---|---|---|
| claim* | string | One factual sentence to check. |
| sources | array | Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type "caller". The response lists what was used in sources_used. |
| sources_only | boolean | Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array. |
{
"type": "object",
"required": [
"claim"
],
"properties": {
"claim": {
"type": "string",
"examples": [
"The Eiffel Tower is in Paris."
],
"minLength": 1,
"description": "One factual sentence to check."
},
"sources": {
"type": "array",
"items": {
"type": "object",
"anyOf": [
{
"required": [
"url"
]
},
{
"required": [
"text"
]
}
],
"properties": {
"url": {
"type": "string",
"format": "uri",
"maxLength": 2048,
"description": "Public https URL. Fetched with a 3.5 s timeout and a 512 KB cap; http, file and other schemes, private / loopback / link-local / metadata addresses, IP-literal hosts, custom ports and URLs with credentials are rejected (HTTP 400, not charged). With text, it is only the citation link."
},
"text": {
"type": "string",
"maxLength": 20000,
"minLength": 1,
"description": "Source text to check the claim against (up to 20,000 characters). When given, no fetch is made."
},
"title": {
"type": "string",
"maxLength": 200,
"description": "Optional title shown in citations."
}
},
"description": "One source: {url} for a public https page we fetch, or {text, title?, url?} for text you already have.",
"additionalProperties": false
},
"maxItems": 10,
"description": "Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type \"caller\". The response lists what was used in sources_used."
},
"sources_only": {
"type": "boolean",
"default": false,
"description": "Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array."
}
},
"additionalProperties": false
}