Summary
Connects Claude to a live fact-checking API that returns structured verdicts (CURRENT, OUTDATED, DISPUTED, UNVERIFIABLE) with confidence scores and supporting sources. Exposes four tools: verity_verify for single claims, verity_deep_check for thorough multi-angle verification, verity_batch for up to 10 claims at once, and verity_agent for natural language queries. Each call costs between 0.10 and 0.75 USDC on Base. Maintains persistent memory across sessions if you pass a consistent caller_id, so it remembers what you've already checked. Useful when you need to validate information against current web sources or catch outdated claims in documentation and content.
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Public tool metadata for what this MCP can expose to an agent.
4 tools
verity_verifyVerify a claim, URL, or statement against live web sources. Returns CURRENT/OUTDATED/DISPUTED/UNVERIFIABLE verdict, confidence 0–100, sources, and what has changed. 0.10 USDC per call.2 params
Verify a claim, URL, or statement against live web sources. Returns CURRENT/OUTDATED/DISPUTED/UNVERIFIABLE verdict, confidence 0–100, sources, and what has changed. 0.10 USDC per call.
Parameters* required
caller_idstringOptional stable ID to activate persistent memory across calls.
claimstringThe claim, URL, or content to verify. E.g. 'Is GPT-4 still the most capable AI model?' or 'https://example.com/article'
verity_deep_checkThorough multi-angle verification with advanced search depth. Cross-references 5+ angles and authoritative sources. Higher confidence result for high-stakes fact-checks. 0.50 USDC per call.2 params
Thorough multi-angle verification with advanced search depth. Cross-references 5+ angles and authoritative sources. Higher confidence result for high-stakes fact-checks. 0.50 USDC per call.
Parameters* required
caller_idstringOptional stable ID for persistent memory.
claimstringThe claim to deeply verify. E.g. 'Did the 2024 US election results change after court challenges?'
verity_batchVerify up to 10 claims in one call. Returns an array of verdicts. Use for content audits and fact-check pipelines. 0.75 USDC for the batch.2 params
Verify up to 10 claims in one call. Returns an array of verdicts. Use for content audits and fact-check pipelines. 0.75 USDC for the batch.
Parameters* required
caller_idstringOptional stable ID for persistent memory.
claimsarrayArray of claims to verify. Max 10.
verity_agentNatural language fact-checking. Ask anything: 'Is this still true?', 'When was this last updated?', 'Check this URL'. VERITY selects the right strategy automatically. 0.10 USDC per call.2 params
Natural language fact-checking. Ask anything: 'Is this still true?', 'When was this last updated?', 'Check this URL'. VERITY selects the right strategy automatically. 0.10 USDC per call.
Parameters* required
caller_idstringOptional stable ID for persistent memory.
querystringNatural language fact-check request. E.g. 'Is Elon Musk still the richest person in the world?'
VERITY — Real-Time Fact-Checking Agent
Real-time fact-checking and data freshness agent. Verifies claims, URLs, and content against live web sources. Returns structured verdicts with confidence scores, what has changed, and supporting sources.
Verdicts
| Verdict | Meaning |
|---|---|
CURRENT | Claim is accurate and up to date |
OUTDATED | Claim was true but has since been superseded |
DISPUTED | Sources disagree — no clear consensus |
UNVERIFIABLE | No usable sources found |
MCP Setup (Claude Desktop / Cursor)
{
"mcpServers": {
"verity": {
"command": "npx",
"args": ["verity-mcp"],
"env": {
"VERITY_PRIVATE_KEY": "0x..."
}
}
}
}
Get USDC on Base at coinbase.com/wallet.
Tools
| Tool | Description | Price |
|---|---|---|
verity_verify | Verify a claim or URL against live sources | 0.10 USDC |
verity_deep_check | Multi-angle thorough verification | 0.50 USDC |
verity_batch | Verify up to 10 claims at once | 0.75 USDC |
verity_agent | Natural language fact-checking | 0.10 USDC |
check_credits | Remaining balance for a PayGated pg_ key | free |
API
POST https://verity.basechainlabs.com/api/verify
Authorization: x402 (USDC on Base)
{
"claim": "Is GPT-4 still the most capable OpenAI model?",
"caller_id": "my-agent-id"
}
Response:
{
"verdict": "OUTDATED",
"confidence": 91,
"summary": "GPT-4 has been superseded by GPT-4o and o3.",
"what_changed": "OpenAI released GPT-4o (May 2024) and o3 (late 2024).",
"sources": [{ "url": "...", "title": "...", "published_date": "2025-01", "supports": "CONTRADICTS" }],
"checked_at": "2026-05-11T09:00:00Z",
"recommendation": "Update any content referencing GPT-4 as the most capable model."
}
Persistent Memory
Pass a consistent caller_id on every call. VERITY remembers topics you've checked, domains you monitor, and previous results — no re-sending context.
A2A Agent Card
GET https://verity.basechainlabs.com/api/agent?agent-card=true
Built by BaseChain Labs
Making changes (maintainer guide)
Where things live
| Thing | Where |
|---|---|
| The agent's brain | src/agent.ts (system prompt, orchestration), src/tools.ts (fact-checking: Tavily search + Claude verdicts) |
| API endpoints | one file per route under api/: agent (paid A2A entry), verify, deep-check, batch-verify, mcp, checkout, stripe-webhook, recover-key, plus the cron-check-deps and daily-summary crons |
| Payment gate | api/_x402-gate.ts: unpaid POSTs get HTTP 402 with the price and the Bazaar listing; GET returns the agent card |
| Public page | public/index.html (plain HTML). Agent card: public/.well-known/agent.json |
| Marketplace seller | seller-v2.mjs + Dockerfile + railway.json, the Virtuals ACP seller on Railway. Its keyring lives on a Railway volume; keyring.json and keyring.key are runtime files and gitignored |
| Secrets | hosting environment variables only. Never in a file, never in a commit |
How a change goes live
There is no test suite and no CI on this repo. A push to main is the deploy.
- Edit, then type-check:
npx tsc --noEmit -p . - Commit and push to
main. Vercel builds and deploys production from the GitHub integration. - Confirm the newest production deployment carries your commit SHA and the endpoint answers:
curl -s https://verity.basechainlabs.com/.well-known/agent.json | head -c 300 - A push also redeploys the Railway seller. Confirm its log shows it connected afterwards.
Because there are no tests, prove a change on the live endpoint with a read-only call before calling it done. Never make a paid call (x402 or Stripe) just to test.
Things that bite
- Prices live in four places that must stay in sync:
public/index.html, the 402 body inapi/_x402-gate.ts, the Virtuals ACP offerings, and the npm package README. - Agentic.market's "Validate endpoint" tool: use POST. GET returns the agent card (200) by design and the validator then says "no x402 setup".
- Tavily is the search backend. If verifications start failing, check the Tavily credit first.
- Removing the Railway volume wipes the seller's keyring on the next redeploy and takes it offline.
Featured
Keeps your Mac awake while Claude Code, Codex or Cursor works. Lets it sleep when they are done.
Try free for 7 days →Block distracting apps from your iPhone permanently without a 3rd party app. Free and open source.
Block now (100% free) →Notes, actions and memory. Without a meeting bot. First month 100% off.
Download for free →belt cli automatically finds the best tools and skills for your agent. image, video, music, tts...
one prompt install →Free an open-source skills that make AI coding agents easier to understand, verify, and control.
Download for free →Connect your Claude agent to live crypto prices and trading routes via 1inch
Get the MCP →Configuration
VERITY_PRIVATE_KEY*secretBase wallet private key (0x...) — used to sign x402 payments in USDC on Base. Per-call: 0.10 USDC (verify), 0.50 USDC (deep-check), 0.75 USDC (batch).