Claude/Desktop/Extension

• Getting Started with Local MCP Servers on Claude Desktop

  • Overview

    • Desktop extensions let Claude directly interact with apps, data, and tools on your computer via local MCP servers packaged as single-click installs (like browser extensions).
    • Location: Claude/Desktop → Settings > Extensions
    • Packages use the .mcpb (MCP Bundle) format; legacy .dxt files still work.
    • Help center overview also in Install Claude Desktop (desktop extensions section).

  • Relation to connectors

    • Remote connectors (Slack, Linear, Google Drive, custom remote MCP) are configured under Customize > Connectors or Settings > Connectors — see Claude/Desktop/Connector.
    • Desktop extensions install here (Settings > Extensions) but enabled tools appear in the chat + → Connectors menu alongside remote connectors.
    • Notable extensions often enabled from the directory: Filesystem, Control Chrome, pdf-viewer (summarized on the Connector page).

  • What desktop extensions are

    • Streamlined install and management of local MCP servers—no manual JSON config or dependency wrangling for typical users.
    • Model Context Protocol (MCP): open protocol connecting LLM apps to external data sources and tools.
    • Each extension bundles server code, dependencies, and manifest.json metadata; Claude Desktop supplies built-in Node.js, automatic updates (directory extensions), and OS keychain storage for secrets.
    • Curated directory in-app (Anthropic-reviewed); developers can submit via desktop extensions interest form.
    • Architecture post: Claude Desktop Extensions (Anthropic Engineering)

  • Installing from the directory

    • 1. Settings > Extensions → Browse extensions
    • 2. Choose an Anthropic-reviewed extension → Install
    • 3. Configure required settings (e.g. API keys) in the UI
    • 4. Extension is available in conversations automatically

  • Installing custom extensions

    • Settings > Extensions → Advanced settings → Extension Developer → Install Extension…
    • Select a .mcpb file and follow prompts
    • Developer docs: anthropics/mcpb

  • Admin controls (Team and Enterprise)

    • Owners and Primary Owners can:
      • Enable or disable public desktop extensions per org security standards
      • Upload custom extensions for one-click team install
    • Customize registries: add needed extensions, remove others
    • Allowlist: manage which extensions members can use — Enabling and using the desktop extension allowlist
    • Custom uploads: org-specific workflows not in the public directory (same Extension Developer flow)

  • Enterprise policy controls

    • Machine-level policies override in-app blocklist/allowlist. For in-app allowlist, do not set isDesktopExtensionEnabled and isDesktopExtensionDirectoryEnabled to "false".
    • System policy reference: Enterprise configuration for Claude Desktop
    • Safeguards (preview): OS keychain for secrets, automatic updates, audit installed extensions; Group Policy (Windows) / MDM (macOS), pre-install approved extensions, blocklist publishers, disable directory, private registries

  • Troubleshooting

    • Extension won't install

      • Latest Claude Desktop version
      • Re-download if file corrupted
      • Sufficient disk space

    • Installed but tools unavailable

      • Restart Claude Desktop
      • Check extension configuration for missing required fields
      • Verify API keys / credentials

    • Configuration issues

      • Settings > Extensions → open extension → review settings
      • Required fields complete; file paths exist and are accessible

    • Permission or security errors

      • macOS: System Preferences > Security & Privacy
      • Windows: Claude Desktop permissions for required directories
      • Enterprise: verify org policies allow desktop extensions

  • Developer FAQ

    • Check MCP connection: chat + → Connectors (servers and tools); or Developer settings under Desktop app (status and logs)
    • Convert existing MCP server: add manifest.json → mcpb pack → MCPB documentation
    • Languages: Node.js, Python, binary MCP servers; Claude Desktop includes Node.js (no separate Node install required)
    • Sensitive config: "sensitive": true in manifest.json → encrypted in OS secure storage (Keychain / Credential Manager)
    • Private distribution: share .mcpb directly; submit to official directory for broader reach
    • Debug: debug logging in settings, extension logs in Extensions panel, MCP debugging guide
    • Updates: directory extensions auto-update by default; private .mcpb installs are manual

  • MCPB package format (summary)

    • .mcpb: ZIP archive with required manifest.json plus server implementation and bundled dependencies
    • Before extensions: terminal install, manual claude_desktop_config.json, dependency conflicts, no discovery
    • After: download/double-click → Install (no terminal for end users)
    • Tooling: npm install -g @anthropic-ai/mcpb → mcpb init → mcpb pack
    • Manifest highlights: user_config drives settings UI; ${user_config.*}, ${__dirname}, ${HOME} template substitution; optional tools / prompts declarations
    • Open ecosystem: MCPB spec and toolchain open-sourced for portability beyond Claude Desktop

  • Learn more about MCP

    • MCP Quickstart Guide
    • Model Context Protocol GitHub
    • Guide to debugging MCP integrations
    • Enterprise deployment: Deploying enterprise-grade MCP servers with desktop extensions