Ultrathink MCP Server

Save and search your Ultrathink knowledge base from any MCP-compatible client: Claude Desktop, Claude Code, Cursor, Zed and more.

Ultrathink is a second-brain app that captures notes, links, screenshots, AI conversations, PDFs and more into a single AI-searchable knowledge base.

New: the hosted Ultrathink MCP server

Ultrathink now runs its own MCP server online, so there is nothing to install. It has more tools than this package: search, read an entry in full, related entries, recent changes, everything about a person or a topic, lists of your topics and people, and adding and updating entries.

Connect Claude Code with one command, using a device key with API access:

claude mcp add --transport http ultrathink https://us-central1-ultrathink-50f7f.cloudfunctions.net/mcp --header "Authorization: Bearer YOUR_DEVICE_KEY"

Any MCP client that supports remote servers over HTTP with a header can use the same address. Setup, tools and troubleshooting are in the MCP server guide.

The hosted server is the recommended way to connect. This package keeps working, with the two tools below, for clients that only run local servers.

Related MCP server: open-brain-mcp

This package

It gives your AI assistant two tools:

• ultrathink_save: store a note, link, idea or snippet in your knowledge base

• ultrathink_search: natural-language search across everything you've captured

Install

npm install -g ultrathink-mcp

Or use directly with npx ultrathink-mcp (no install needed).

Configuration

You need an Ultrathink device key. Get one at tryultrathink.com.

Set as environment variables:

export ULTRATHINK_DEVICE_KEY="your-device-key-here"

Optional:

export ULTRATHINK_API_BASE="https://us-central1-ultrathink-50f7f.cloudfunctions.net"  # default
export ULTRATHINK_SOURCE="claude-code"  # tag entries with a source label

Use with Claude Code

Add to your ~/.claude.json mcpServers:

{
  "mcpServers": {
    "ultrathink": {
      "command": "npx",
      "args": ["-y", "ultrathink-mcp"],
      "env": {
        "ULTRATHINK_DEVICE_KEY": "your-device-key-here"
      }
    }
  }
}

Use with Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "ultrathink": {
      "command": "npx",
      "args": ["-y", "ultrathink-mcp"],
      "env": {
        "ULTRATHINK_DEVICE_KEY": "your-device-key-here"
      }
    }
  }
}

Tools

ultrathink_save

Save an entry to your Ultrathink knowledge base.

Inputs:

• title (required): title of the entry

• notes: main content for most entries

• content: full content for longer entries

• type: one of note, link, idea, snippet, para, chatgpt, claude, perplexity, notion, long-note, profile. Default: note

• url: required when type is link

• visibility: private (default) or org

ultrathink_search

Natural-language search across your Ultrathink knowledge base. Returns an AI-generated answer based on stored entries.

Inputs:

• query (required): natural-language search query

• entityFilter: optional, one of project, task, knowledge

Licence

MIT