Use Lenz inside Claude or ChatGPT.
Connect Lenz once, then ask the chat to check a claim. The answer comes back in the thread — a verdict, a score from 1 to 10, and the independent sources behind it. No key for either. Claude takes one click; ChatGPT takes a few more steps, and that route is in beta.
Claude
Desktop · web · mobile
One sign-in. No key to paste.
Open the Lenz connector page and click Connect to Claude.
Complete Sign in with Lenz. The connection is authorized against your Lenz account, so there is no key to paste and nothing is written to a file.
Claude Desktop, claude.ai and the Claude mobile apps share one account, so connecting once covers all three.
Settings → Extensions → Browse extensions, search for Lenz and click +, then complete the sign-in prompt. Same connection, same account.
Ask Claude:
check with Lenz that the Great Wall of China is visible from space with the naked eye
You get a verdict, a score from 1 to 10, and the citations behind it. Naming Lenz is what makes the assistant reach for it rather than answer from memory.
ChatGPT Beta
chatgpt.com · Plus or Pro, or a workspace · Developer mode (beta)
One sign-in. No key to paste.
At this time, ChatGPT connects to Lenz as a custom app through OpenAI's Developer mode. You set it up once on chatgpt.com, on a Plus or Pro account, and sign in with your Lenz account; there is no key to paste.
Settings → Plugins → turn on Developer mode, at the bottom. ChatGPT warns that this is elevated risk; that applies to any custom app. Lenz checks claims and changes nothing.
Plugins → Browse plugins → + next to Search. Name it Lenz, paste
https://lenz.io/mcpas the server URL, and choose OAuth under Authentication. Leave the advanced OAuth settings as they are, tick I understand and want to continue, and click Create.Click Sign in with Lenz in the popup and authorize.
Click Try in Chat. In every later chat, + and tick Lenz: a custom app is off by default in each conversation.
Once, by an owner or admin. Workspace settings → Apps → + Create, and confirm Enable developer mode. Fill in the same form with OAuth under Authentication, then open Drafts, click Publish, set who can use it, and Publish again.
Then, each person. Settings → Plugins → Lenz → Connect, sign in with Lenz, and click Try in Chat.
In the chat, + → tick Lenz (Try in Chat has it ticked already), then ask:
check with Lenz that the Great Wall of China is visible from space with the naked eye
You get a verdict, a score from 1 to 10, and the citations behind it. Lenz has to be ticked in each new chat; naming it in the question is what makes ChatGPT use it rather than answer from memory.
What you can ask it
Name Lenz in the question. That is what makes the assistant reach for it rather than answer from its own knowledge — and Lenz answers with a verdict, a score, and the sources it read. In ChatGPT, tick Lenz under + in the chat first.
- “Check the figures in this draft with Lenz before I send it.”
- “Is that last answer right? Check it with Lenz.”
- “Use Lenz to pull the factual claims out of this press release and check each one.”
- “What sources did Lenz find for that verdict, and do any of them disagree?”
A fast pass over several claims comes back in about ten seconds. One claim run through the full pipeline — framing, research, debate, panel review, conclusion — takes about ninety, and returns the citations and the reasoning behind the verdict with it.
What it costs
Free to start, no card required: 100 credits a month, which is 100 fast checks or 10 run through the full pipeline. Checks from the chat draw on the same credits as everything else on your account.
Questions
No, for either. You sign in with your Lenz account and the connection is authorized against it — on Claude through Connect to Claude, on ChatGPT through Sign in with Lenz when the app is created. If you do not have a Lenz account yet, the sign-in creates one.
Yes. One Lenz account, one balance. A check you run from Claude draws on the same credits as one you run on the site or through the API.
It is where OpenAI puts custom apps — servers that are not yet in the ChatGPT app directory. It exists on chatgpt.com, on a Plus or Pro account, or in a Business, Enterprise or Edu workspace where an owner or admin publishes the app once. ChatGPT shows an elevated-risk warning when you turn it on; that applies to any custom app, and Lenz checks claims and changes nothing. Once it is on, Lenz is an app you tick in each new chat.
Yes. A claim submitted through the connector is private to your account, the same as one submitted through the API. Claims you check on the Lenz website work the other way round — they are public by default, and you can switch any one of them to private on its own page.
Other ways to connect Lenz
- MCP server → — the same server for coding tools: Claude Code, Codex, Cursor, or any MCP client. Point it at
lenz.io/mcpwith a Bearer header. - n8n node → and Zapier app → — a fact-check step inside a workflow, no code.
- All integrations → — WhatsApp, the CLI, and the REST API with typed Python and TypeScript SDKs.
Resources
Check a claim without leaving the chat.
Free tier, no card required.