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Lenz Fact-Check MCP Server

answering

Lenz Fact-Check is answering right now. Last checked 2 min ago. Last commit 21 Sep 2026.

Check the factual claims in a draft or an answer: a quick verdict, or a deep check with sources.

Uptime history 51 days of history · worst day 98%
51 days agonow
100.0%
Uptime 24h
91 of 91 checks
Tools
hidden behind auth
301 ms
Response time
average over 24h
0
Stars
last commit 21 Sep 2026

What the code does

We read the source, 9 h ago · rules 3dff92dd89df

Capabilities

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

Page executes code built at runtime src/lenz_mcp/card/dist-dev/card-dev.html:238
…ked"?_=p:l&&typeof p!="function"||f[u]===p||de(e,u,p,f[u],s);if(h)l||m&&(h.__html==m.__html||h.__html==e.innerHTML)||(e.innerHTML=h.__html),t.__k=[];else if(m&&(e.innerHTML=""),qt(t.type=="template"?e.content:e,ve(c)?c:[c],t,r,n,y=="foreignObject"?"http://www.w3.org/1999/xhtml":s…

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

This code can reach further than it looks

We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.

Three servers free · no card

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 2 min ago.

run in your terminal
claude mcp add fact-check --transport http https://lenz.io/mcp
~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "fact-check": {
      "url": "https://lenz.io/mcp"
    }
  }
}
~/.codex/config.toml
[mcp_servers.fact-check]
url = "https://lenz.io/mcp"
.cursor/mcp.json
{
  "mcpServers": {
    "fact-check": {
      "url": "https://lenz.io/mcp"
    }
  }
}
.vscode/mcp.json
{
  "mcpServers": {
    "fact-check": {
      "url": "https://lenz.io/mcp"
    }
  }
}

This endpoint answered with an authorization challenge. The server is running, and it signs you in through your browser: there is no API key to paste.

Endpoints

URLTransportStateLatencyChecked
https://lenz.io/mcp streamable-http sign-in 262 ms 2 min ago

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Lenz Fact-Check — questions

Answers built from our own checks of this server.

Why is there no tool list for Lenz Fact-Check?
The server answered our handshake with an authorization challenge, so it is running — but it will not describe its tools to an anonymous client. To see them you need to connect with your own credentials. We record it as alive, not as broken: 100.0% of checks in the last 24 hours got a reply.
Is Lenz Fact-Check working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 301 ms. The bar chart above shows every period we have measured.
How do I connect Lenz Fact-Check?
Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address. You sign in through your browser once and the client keeps the session: no key to copy, and it refuses anonymous clients.
How do you sign in to Lenz Fact-Check?
No API key is involved. Lenz Fact-Check answers our knock with an OAuth challenge, so you authorise it once in your browser and the client keeps the session. That is also why we see no tool list: it will not describe itself to an anonymous client, and that is the server working as intended, not a fault.
How fast is Lenz Fact-Check?
It answers our handshake in 301 ms on average, which is faster than 53% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.
Is Lenz Fact-Check open source?
Yes — it is published under the Apache-2.0 licence, written in Python and 0 stars on GitHub. The source link is on this page, so you can read exactly what it does with your data before you connect it.