For developers

Connect Lenz to your AI client.

Lenz is a remote Model Context Protocol server. Add it to Claude Desktop, Claude Code, Cursor, or any MCP client, and your assistant can fact-check a claim against independent sources — a sourced verdict with citations, right inside the chat.

Nothing to install. It's hosted at lenz.io/mcp over Streamable HTTP, and it authenticates with the same lenz_… API key as the REST API — so there's no separate signup.

Get a free API key → View on GitHub API reference

Add the server

Point your client at https://lenz.io/mcp with a Bearer header. Set LENZ_API_KEY in your environment first — grab a free key →

Any MCP client .mcp.json

// add to your client's MCP config
{
  "mcpServers": {
    "lenz": {
      "type": "http",
      "url": "https://lenz.io/mcp",
      "headers": {
        "Authorization": "Bearer ${LENZ_API_KEY}"
      }
    }
  }
}

Claude Code one command

# register the remote server
$ claude mcp add --transport http lenz \
    https://lenz.io/mcp \
    --header "Authorization: Bearer ${LENZ_API_KEY}"

# then, in any session:
> verify: "The Great Wall is visible from space"

Claude Desktop config file

# same JSON as "Any MCP client", in:
# macOS   ~/Library/Application Support/
#           Claude/claude_desktop_config.json
# Windows %APPDATA%\Claude\
#           claude_desktop_config.json
# Restart Claude Desktop to load it.

Full setup notes, per-client quirks, and examples live in the lenz-mcp repo →

What your assistant can do

Six tools, same depth ladder as the API. Ask in plain language; the client picks the tool.

  • assess — fast 3-model panel verdict in ~5-10s.
  • verify — the full 8-model pipeline with citations (~90s).
  • get_verification — poll a running verify by task id.
  • ask — a grounded follow-up question about a completed verify, answered from its full evidence.
  • select — resolve an ambiguity when a claim could mean more than one thing.
  • check_usage — remaining quota and plan.

These are tools, not slash commands. In a client like Claude Code, just ask in plain language — “assess whether the earth is flat with Lenz” — and the assistant calls the right tool.

Prefer to call it in code instead? The same primitives are a REST API and typed Python / TypeScript SDKs — see the developer docs →

Pricing

Start free, no card required. The MCP server shares your API quota — same key, same limits.

Free

$0

/extract · 1,000/day
/assess · 100/mo
/verify · 10/mo
/ask · 20/mo

Prototype today, zero spend. No card required.

Developer

$99/mo

/extract · 1,000/day
/assess · 5,000/mo
/verify · 500/mo
/ask · 1,000/mo

Self-serve. $999/yr annual.

Scale

$399/mo

/extract · 1,000/day
/assess · 20,000/mo
/verify · 2,000/mo
/ask · 4,000/mo

$3,990/yr annual. For production integrations.

Enterprise

Volume beyond Scale, SLAs, white-label, custom integration support.

Talk to us →

Compare all plans on the plans page →

Frequently asked questions

A remote Model Context Protocol server hosted at lenz.io/mcp. It exposes Lenz's fact-checking pipeline as MCP tools, so an AI client like Claude Desktop, Claude Code, or Cursor can verify a claim against independent sources and get a sourced verdict — without leaving the chat.

No. The server is remote, over Streamable HTTP. Point your MCP client at https://lenz.io/mcp with an Authorization: Bearer header carrying your API key. Get a free key at /api-integration.

Six: assess (fast 3-model verdict), verify (full 8-model pipeline with citations), get_verification (poll a running verification), ask (grounded follow-up on a completed verification), select (resolve ambiguity in a result), and check_usage (remaining quota).

Yes. The MCP server is a thin proxy over the same public API at lenz.io/api/v1, authenticated with the same lenz_… Bearer key from /api-integration. No separate signup.

Resources

lenz-mcp on GitHub Developer docs API reference Get an API key API terms

Give your assistant a fact-checker.

Self-serve from day one. Free tier, no card required.

Get a free API key →