# Lenz Fact-Check

Validates factual statements and source citations against live web pages. Useful for drafting reports and articles when model output requires independent evidence.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI
- Author: lenzhq
- License: Apache-2.0 · policy=link-only · description only; the file stays with the author
- Source: https://github.com/lenzhq/lenz-mcp
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/mcp/lenz-fact-check

## What it does

Lenz runs as a hosted endpoint at `https://lenz.io/mcp` without local runtimes. Communication relies on stateless HTTP using OAuth or an API token. The server handles validation at two speeds: a 15-second multi-model screening via `assess_claim` and an in-depth investigation via `verify_claim`.

The deep check researches public evidence, runs a debate panel, and grades credibility on a ten-point scale. Because clients like Claude Code or Cursor cap tool execution time, long checks return a `submitted` status with a task identifier. Your assistant then polls `get_verification` to retrieve the final verdict and source quotes.

Reference validation runs under `check_citations`. It inspects URLs and DOIs in the draft, confirming whether the cited material actually supports the author's statements.

## Requirements
- Remote server: `https://lenz.io/mcp`

## Install

### Claude Code (native platform)

**Platform CLI: remote server**
```bash
claude mcp add --transport http fact-check https://lenz.io/mcp
```

### Codex

**Platform CLI: remote server**
```bash
codex mcp add lenz-fact-check --url https://lenz.io/mcp
```

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "lenz-fact-check": {
            "url": "https://lenz.io/mcp"
        }
    }
}
```

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "lenz-fact-check": {
            "type": "http",
            "url": "https://lenz.io/mcp"
        }
    }
}
```

### Gemini CLI

**Platform CLI: remote server**
```bash
gemini mcp add -t http lenz-fact-check https://lenz.io/mcp
```

## When to use it
- verify disputed factual claims against independent web sources
- confirm whether links and DOIs support the draft sentences citing them
- retrieve verifiable quotations and confidence scores for draft statements
- generate corrected sentence rewrites for refuted assertions

## Example prompts
- Run a quick fact check on the claims in this section using `assess_claim`.
- Perform a deep verification of the revenue figures with `verify_claim` and pull source quotes.
- Check whether the bibliography links actually back up the argument via `check_citations`.

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