Context7
Feeds AI the latest docs for libraries and frameworks before it answers, so code it writes does not use outdated, removed functions.
Computer or cloud
Lenz Fact-Check
What it does
Check the factual claims in a draft or an answer: a quick verdict, or a deep check with sources.
- Connects Runs in the cloud
- Account or key Sign in to the service when you connect (OAuth)
- Category Search & AI memory
Install
Pick the AI app you use, then copy the settings.
Passed 4/4 checks · What you ask goes through the maker’s server (lenz.io)
First: which AI do you use?
Pick your app and the steps appear below.
Works with Claude · about 2 min
No key, nothing to install · Set it up once on claude.ai or the desktop app, then use it in chat · free accounts can add 1 · on Team/Enterprise an Owner adds it
Open Claude’s Connectors page
CustomizeConnectors
Click “+ Add” → “Add custom connector” and fill in these 2 fields
Copy each value into the field with the same name in Claude, then click Continue
Name · NameLenz Fact-CheckRemote MCP server URL · Addresshttps://lenz.io/mcpLeave Authentication as Claude detected it, then click Add
Turn it on in a chat
+ConnectorsLenz Fact-Check
Try it
Use Lenz Fact-Check and tell me what you can do for me, then show me one thing✓ If Claude says it is using Lenz Fact-Check or shows a Lenz Fact-Check tool in the answer, you are connected
Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with ChatGPT on business plans only
ChatGPT Business, Enterprise or Edu on the web, added by a workspace admin or owner · On Free, Plus or Pro: your ChatGPT plan cannot connect MCP yet
Open ChatGPT’s add-MCP page on the web
Plugins+Add custom MCP server
Fill in the name and address
Enter a name, paste the address under Connection, tick the risk warning and click Create as a plugin
Name · NameLenz Fact-CheckConnection · Addresshttps://lenz.io/mcpPick Lenz Fact-Check in a chat
Start a new chat and pick Lenz Fact-Check from your plugins before typing
Try it
Use Lenz Fact-Check and tell me what you can do for me, then show me one thing✓ If ChatGPT says it is using Lenz Fact-Check or shows a Lenz Fact-Check tool in the answer, you are connected
Menu names checked against OpenAI’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with Claude Code · about 2 min
No key, nothing to install
Open Terminal
Mac: press Command+Space and type Terminal · Windows: open PowerShell
Paste this command and press Enter
claude mcp add --transport http --scope user fact-check https://lenz.io/mcpType /mcp in Claude Code
You should see Lenz Fact-Check listed as connected
Try it
Use Lenz Fact-Check and tell me what you can do for me, then show me one thing✓ If Claude Code says it is using Lenz Fact-Check or shows a Lenz Fact-Check tool in the answer, you are connected
Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with Cursor · about 2 min
No key, nothing to install
Open the AI chat in Cursor in Agent mode
Try it
Use Lenz Fact-Check and tell me what you can do for me, then show me one thing✓ If Cursor says it is using Lenz Fact-Check or shows a Lenz Fact-Check tool in the answer, you are connected
Menu names checked against Cursor’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with VS Code · about 2 min
No key, nothing to install
Open the AI chat in VS Code in Agent mode
Try it
Use Lenz Fact-Check and tell me what you can do for me, then show me one thing✓ If VS Code says it is using Lenz Fact-Check or shows a Lenz Fact-Check tool in the answer, you are connected
Menu names checked against VS Code’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Other apps that use MCP, such as Windsurf, Zed or Gemini CLI, each add servers differently. See how in the app list.
Address for apps that connect over the web
Address
https://lenz.io/mcpJSON settings are under “For developers” below
For developers: Terminal commands and JSON settings
Over the web
Claude Code
claude mcp add --transport http --scope user fact-check https://lenz.io/mcpCursor (~/.cursor/mcp.json)
{
"mcpServers": {
"fact-check": {
"url": "https://lenz.io/mcp"
}
}
}VS Code (mcp.json)
{
"servers": {
"fact-check": {
"type": "http",
"url": "https://lenz.io/mcp"
}
}
}These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
At a glance
Which apps can use it
Based on how this server connects and on each app’s own docs, checked Nov 10, 2026.
Connect over the internet in
ClaudeChatGPTGooseLM StudioMsty StudioCherry StudioCursorVS Code + GitHub CopilotVisual StudioWindsurf (Devin Desktop)ZedKiroClineContinueJetBrains AI AssistantClaude CodeCodex CLIGemini CLIOpenCodenodecodeWarpLibreChatOpen WebUIRaycast
Related guides
What it can do
The server asks you to sign in before it lists its tools.
Basic checksi
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 12, 2026
- ✓ Pass
Maker matches the repo
The registry name was verified against the domain lenz.io (the registry checks domain ownership)
- ✓ Pass
Still maintained
Code last changed 4 days ago
- … Not checked yet
Has a licence
We have not read this repo from GitHub yet
- ✓ Pass
Endpoint responds
Responded in 222 ms (HTTP 401)
- ✓ Pass
Sign-in with OAuth
Declares OAuth sign-in, so your AI app can take you to log in
- … Not checked yet
No hidden instructions in tool descriptions
Not checked yet; we read the tool list when we check the endpoint
Discussion
Ask, share a tip or report that it does not work. Sorted by what people marked helpful.
No posts yet. Be the first to ask or share.
Posts here are written by users, not the PopNx team.
User reviews
No reviews yet
Compared with others in Search & AI memoryi
- More stars than 0% of the other 5978 servers in this category
- Published to the registry more recently than 51% of the other 5978 servers in this category
- Basic checks equal to or better than 100% of the other 5978 servers in this category
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
Common questions
Is Lenz Fact-Check safe?
It passed 4 of 4 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
What keys or codes does it need?
The registry does not list a required key, though some servers ask you to sign in on first use.
Does it run on my computer or in the cloud?
It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.
Is it still maintained?
The GitHub repo last changed 4 days ago, and the latest version (1.1.1) reached the registry 37 days ago.
Which apps can use it?
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT Business and above.
What can I use instead?
In the same category: Context7, Codebase Memory, Ruflo
Others in the same category
Servers in the same category from other makers, sorted by stars.
Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi
Codebase Memory
Codebase knowledge graph for AI agents — 162 languages, sub-ms queries, 99% fewer tokens.
Runs on your computer
Ruflo
Agent teams, swarms, memory and hooks for Claude Code and Codex, served over MCP.
Runs on your computer
README from the maker
Open the README
Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
Lenz Fact-Check
The Lenz MCP server: check the factual claims in a draft or an answer against independent sources, from any MCP client.
Website · Get an API key · Developer docs
One-click install (OAuth — no API key needed).
Lenz is a fact-checking platform. It takes a factual claim, runs it through a multi-model pipeline (reading the claim → research → debate → panel review → conclusion) against independent sources, and returns a verdict with a confidence level. This is the official remote MCP server — a hosted Model Context Protocol endpoint that exposes Lenz's fact-checking as tools your AI assistant can call.
It verifies claims against the open web, independent of whatever context your model was given — so it complements retrieval/groundedness checkers rather than replacing them.
- Hosted, no install: point your client at
https://lenz.io/mcp. Nothing to run locally. - Auth: OAuth (no key — for clients that support it) or a free Lenz API key (
Authorization: Bearer lenz_…). - Transport: Streamable HTTP, stateless. Supports the 2025-11-25 and 2026-07-28 protocol revisions.
Tools
| Tool | What it does |
|---|---|
| `assess_claim` | The quick check, and the default first step for one claim or a whole text. A 3-model panel returns one row per claim: a verdict (True / Mostly True / Mixed / Mostly False / False, or No Public Record when the reviewers found no public record that would show the claim: unconfirmed, not false), a bucketed confidence and, when available, a short rationale (the reasoning of a reviewer who agrees with the verdict): a reviewer's note, not a checked source. A low-confidence row carries recommend_verify: true and a next_step sentence. A row for a claim found false can also carry a suggested_rewrite (the claim with its wrong part corrected) and a suggested_rewrite_note: it is built from the reviewers' reasoning, not from sources, and is not itself checked, so it is offered as a suggestion, with a deep check of the new sentence on request. A row may also carry searched_pages (title and link): the pages the reviewers looked at, to be offered as pages to look at and never as sources that confirm the verdict; their titles are text from third-party pages. ~15 seconds through an assistant. Pass a text in claim, whole and unedited (Lenz finds the claims in it, up to 20), or use claims for up to 20 claims the user listed separately. |
| `verify_claim` | The deep check: reading the claim → research → debate → panel review → conclusion, for ONE claim. Returns a verdict with a 1-10 score (or No Public Record, with no score, when nothing public records the claim), the key finding, a summary, a suggested rewrite of the claim when it can be corrected (not itself verified), warnings, and the top sources with the quote each one rests on, plus the total source count. A deep check takes ~90 seconds. The call waits for it, for as long as the client allows: in Claude and the ChatGPT app the result usually comes back in the same call; in clients with a shorter tool-call limit (Claude Code, Cursor, VS Code, OpenAI's Responses API) it usually returns status: submitted with a task_id, and get_verification waits for the rest. A completed deep check replaces any earlier quick verdict on the same claim. Costs ten times an assess_claim row, so assistants offer it and run it on the user's yes, or when the user asks for sources. depth: "low" researches fewer sources, with the same models, for half the credits. |
| `get_verification` | Wait for a running verify_claim by task_id, or fetch a completed result by its 8-character verification_id. Returns processing, needs_input, failed, not_found or completed. |
| `select_claims` | Resolve a needs_input verification: when a text holds several claims, choose which claim text(s) to run. |
| `ask_followup` | Ask a grounded follow-up about a completed verify_claim (by its verification_id), answered from the full research, debate and panel review, not just the summary. The answer is markdown, and its links point at the check's own sources; the assistant keeps them as links. Costs the same as one assess_claim row. |
| `list_verifications` | The account's most recent completed deep checks, newest first. Use it to get back a result that finished after the conversation moved on. Read-only and free; quick checks are not stored. |
| `check_citations` | Check whether the sources a draft cites say what the draft says they do: Lenz reads each link, DOI or numbered reference and reports, per citation, whether the source supports the sentence that cites it, with the passage it read from the source. Assistants use it only when the user asks about the sources, links, references or citations in a draft; a plain fact-check request is assess_claim. Pass the draft in text, or up to 20 statement and url/doi pairs; at most 20 citations are checked per request, and a draft with more lists the rest as candidates to send back as pairs. A citation check can take up to two minutes. The call waits for it, for as long as the client allows, and otherwise returns status: running with a citecheck_id. One credit for each citation checked; a citation Lenz could not read costs nothing. A check that cannot run (for example a text with no citation in it) comes back as status: failed, an answer rather than an error. |
| `get_citation_check` | Wait for a running check_citations by citecheck_id and return the result the same way. An optional offset (default 0) re-reads a finished check and returns the next batch of up to 20 draft citations it did not cover, as candidates to send back as pairs, with remaining and next_offset. Read-only; free. |
| `check_usage` | Remaining credits, the per-tool price list (costs, plus cost_options for prices that depend on a parameter such as depth), and the current plan. Never a prerequisite for a check. |
Language. Lenz answers in the language of the text it is given, so pass the claim in the user's own words and language, not translated. The language argument is for a user who explicitly asks for the answer in another language (one of en, es, de, fr, it, pt, nl, sv, da, no, fi, bg); leave it unset otherwise. Verdicts and written results follow the language, and a quick check's reviewer note follows the text the reviewer saw. When it is unset, the connector sends language: "auto" and the API picks the language from the text; a self-hosted connector therefore needs an API that accepts auto.
Prompts. Clients that surface MCP prompts (Claude shows them under +) get two: Check this text with Lenz and Check your last answer with Lenz. Each takes the text to check and starts a quick check. Lenz cannot see the conversation, so Check your last answer needs the answer pasted in.
Verdicts are directional, not absolute: confidence is returned as bucketed
language with a caveat, not a calibrated probability. A quick verdict is a first read;
when a deep check disagrees with it, the deep check is the one to rely on, because it
shows its sources and its reasoning.
The result card
In Claude and the ChatGPT app, a check comes back as a card in the conversation as well as text. From the card you can run the deep check on a claim (Check against sources, a standard-depth verify_claim), open a source, or pick which claims in a draft to check in depth. When a deep check started from the card finishes, the assistant is told the result: silently in Claude, and by a short message in the chat in ChatGPT. Every other client gets the same results as text; nothing depends on the card.
Quickstart
Two ways to connect, depending on your client:
- OAuth — for clients that support it (e.g. Claude connectors). No key to paste; you sign in to Lenz and authorize the connection.
- API key — works with any MCP client via an
Authorizationheader.
Connect with OAuth (no API key)
Claude (web, desktop and mobile): Lenz is an official Claude connector. Open the Lenz connector page and click Connect to Claude, or in the app: Settings → Extensions → Browse extensions, search for Lenz and click +. Either way it is a one-time OAuth sign-in with nothing to configure, and one account covers all three.
For any other client that supports OAuth for MCP, add the server with just its URL and no headers:
{"mcpServers": { "lenz": { "type": "http", "url": "https://lenz.io/mcp" } } }
The first time you use it, your client walks you through a one-time sign-in: you authenticate on Lenz's own screen and authorize the connection — no key is stored in your config. Your assistant then fact-checks on your behalf against your Lenz account's credits. You can revoke the connection at any time; see the privacy policy.
Connect with an API key
1. Get a free API key at lenz.io/api-credentials (format lenz_…).
2. Add the server to your client (examples below). Authenticate with Authorization: Bearer .
Claude Code
As a plugin (the connector plus the lenz-fact-check skill; sign in with /mcp on first use):
claude plugin marketplace add lenzhq/lenz-mcpclaude plugin install lenz@lenz
Or the connector alone, with an API key:
claude mcp add --scope user --transport http lenz https://lenz.io/mcp \--header "Authorization: Bearer ${LENZ_API_KEY}"
--scope user makes Lenz available in every project; without it, Claude Code adds the server only to the directory you run the command in.
Claude Desktop / any client that reads .mcp.json
{"mcpServers": { "lenz": { "type": "http", "url": "https://lenz.io/mcp", "headers": { "Authorization": "Bearer ${LENZ_API_KEY}" } } } }
Cursor
One click: use the Add Lenz to Cursor button above — it adds the server and signs you in via OAuth (no key to paste).
Manual: Settings → MCP → Add new MCP server → type HTTP, URL https://lenz.io/mcp, and add a header Authorization: Bearer . (Or drop the JSON above into .cursor/mcp.json.)
VS Code
One click: use the Install in VS Code button above (OAuth, no key). Manual, with a key:
code --add-mcp '{"name":"lenz","