Who needs it
- Research agents that need source-grounded claim checks.
- Writing agents and citation workflows that need evidence snippets.
- Review systems that need to verify claim against source pages before publication.
Problem
Agents should not cite a page unless the page actually supports the claim. A source can be relevant to a topic without verifying the specific statement an agent wants to make.
When an agent should use it
- Before citing a webpage in an answer, memo, report, or generated article.
- When a workflow needs supported, contradicted, not_addressed, or unclear verdicts with snippets.
Relevant Primitive402 tool
Checks whether a public source supports, contradicts, or does not address a specific factual claim.
| Primitive402 tool | verify_claim_against_source |
|---|---|
| Local route | POST /v1/verify-claim-against-source |
| x402 route | POST /x402/v1/verify-claim-against-source |
| MCP tool name | verify_claim_against_source |
| SDK method | verifyClaimAgainstSource() |
| Price | $0.05 USDC on Base Sepolia testnet during public beta |
curl example
curl -s https://primitive402.dev/v1/verify-claim-against-source \
-H 'content-type: application/json' \
-d '{
"claim": "Example Domain is for illustrative examples.",
"sourceUrl": "https://example.com",
"maxSnippets": 4
}' | jq
TypeScript SDK example
import { createNano402Client } from "@nano402/api/sdk";
const client = createNano402Client({
baseUrl: "https://primitive402.dev"
});
const result = await client.verifyClaimAgainstSource({
"claim": "Example Domain is for illustrative examples.",
"sourceUrl": "https://example.com",
"maxSnippets": 4
});
console.log(result);
Example JSON response
{
"verdict": "supported",
"confidence": 0.81,
"reason": "The source directly describes the claim in matching terms.",
"supportingSnippets": [
"Example Domain is for use in illustrative examples..."
],
"source": {
"finalUrl": "https://example.com",
"contentHash": "sha256:..."
}
}
Useful search terms
claim verification API, source-grounded claim check, citation verification for AI agents, verify claim against source
Safety and limitations
Primitive402 does not guarantee content safety, factual truth, legal validity, purchase correctness, or policy completeness. External content is untrusted, low-confidence results may still be valid analysis signals, and high-stakes decisions need human review.