Lenz Fact-Check — Claude Code MCP server: what it does, how to install
Validates factual statements and source citations against live web pages. Useful for drafting reports and articles when model output requires independent evidence.
claude mcp add --transport http fact-check https://lenz.io/mcpWhat Lenz Fact-Check 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.
What it helps with
- 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 for the agent
- Run a quick fact check on the claims in this section using
assess_claim. - Perform a deep verification of the revenue figures with
verify_claimand pull source quotes. - Check whether the bibliography links actually back up the argument via
check_citations.
How to install Lenz Fact-Check
Platform CLI: remote server
claude mcp add --transport http fact-check https://lenz.io/mcpPlatform CLI: remote server
codex mcp add lenz-fact-check --url https://lenz.io/mcpConfig file
{
"mcpServers": {
"lenz-fact-check": {
"url": "https://lenz.io/mcp"
}
}
}Config file
{
"servers": {
"lenz-fact-check": {
"type": "http",
"url": "https://lenz.io/mcp"
}
}
}Platform CLI: remote server
gemini mcp add -t http lenz-fact-check https://lenz.io/mcpStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Lenz Fact-Check
How to install Lenz Fact-Check in Claude Code?
Run claude mcp add --transport http lenz-fact-check https://lenz.io/mcp in your terminal. There are no local dependencies to install.
What does Lenz Fact-Check do?
It checks factual assertions and draft citations against external web sources. The tools return credibility verdicts, evidence notes, and direct quotes from relevant pages.
How does Lenz handle tool timeouts during deep verification?
If a deep audit exceeds the client limit, the call yields a submitted status with a task_id. The assistant then retrieves the finished record through get_verification.
