Connecting MCP Servers to Claude Desktop

MCP servers are how Claude Desktop connects to the tools you already use -- your calendar, email, file storage, project management software, and more. Think of them as bridges between Claude and your business software. Once a bridge is in place, you can ask Claude to check your calendar, read an email, update a spreadsheet, or post to Slack -- and it does it directly, without you switching applications or copying data manually.

What is MCP?

MCP stands for Model Context Protocol. It is an open standard -- a shared technical language -- that allows AI applications like Claude to communicate with external software services. The key word is "standard": because MCP is a common protocol, any software that supports it can be connected to Claude Desktop using the same configuration pattern. You do not need a bespoke integration for every tool.

An MCP server is a small program that runs on your computer and acts as the go-between. When you ask Claude to "check my calendar for tomorrow", Claude talks to the calendar MCP server, which talks to Google Calendar on your behalf, and brings the result back to Claude. The server handles the translation; you just ask the question.

What you need first

Node.js

Most MCP servers are distributed as Node.js packages. Node.js is a program that runs JavaScript code outside of a web browser. You install it once, and then it handles running MCP servers in the background. Think of it like installing a runtime environment -- similar to how your computer needs Java installed to run Java programs.

Install Node.js from nodejs.org. Download the LTS (Long Term Support) version -- this is the stable, recommended option. The installer walks you through the process; no command line is needed for the installation itself. Once installed, you do not need to think about Node.js again -- it just sits there enabling MCP servers to run.

JSON basics

MCP servers are configured in a JSON file. JSON (JavaScript Object Notation) is a structured text format for settings -- imagine a form where each field has a name and a value, with specific punctuation rules. You will be editing this file to add server entries. The main rules to know:

• Every key and string value is wrapped in double quotes: "key": "value"
• Items in a list are separated by commas -- but the last item in a list has no comma after it
• A missing comma or a stray comma will break the entire file -- the app will silently fail to load any servers
• Validate your file at jsonlint.com any time you are unsure -- paste the contents and it tells you immediately if something is wrong

Configuration file location

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%Claudeclaude_desktop_config.json

If the file does not exist, create it. Claude Desktop reads it on every launch. On macOS, the ~/Library/ folder is hidden by default -- in Finder, press Cmd+Shift+G and paste the path to navigate there directly.

Configuration format

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem",
               "/Users/yourname/Documents"]
    },
    "notion": {
      "command": "npx",
      "args": ["-y", "@notionhq/notion-mcp-server"],
      "env": {
        "NOTION_API_TOKEN": "ntn_xxxxxxxxxxxx"
      }
    },
    "google-calendar": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-google-calendar"],
      "env": {
        "GOOGLE_CLIENT_ID": "your-client-id",
        "GOOGLE_CLIENT_SECRET": "your-client-secret"
      }
    }
  }
}

Each entry in mcpServers specifies:

• command -- the executable that starts the server. Almost always npx, which is a tool that comes with Node.js for running packages without installing them permanently.
• args -- a list of arguments passed to the command, including the server package name (the bit starting with @) and any configuration like a folder path
• env -- environment variables the server needs. This is where API tokens and credentials go. Each service has its own setup process for generating these -- consult the server's documentation.

Worked example: connecting the filesystem server

The filesystem server is the simplest starting point. It gives Claude the ability to read files from a folder you specify -- useful for asking Claude to summarise documents, search through notes, or reference reference material stored on your computer.

Step 1: Open the config file. On macOS, use Finder (Cmd+Shift+G to navigate to the hidden Library path) or open it in your text editor of choice. On Windows, press Win+R, type %APPDATA%Claude, and open the file.

Step 2: Add the filesystem entry. The full config file should look like this (replacing /Users/yourname/Documents with the actual folder path you want Claude to access):

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem",
               "/Users/yourname/Documents"]
    }
  }
}

What each line does:

• "filesystem" -- the name you are giving this server. You choose this; it just needs to be unique within the file.
• "command": "npx" -- tells Claude Desktop to use npx (the Node.js package runner) to start this server.
• "-y" -- tells npx to skip any confirmation prompts and just run.
• "@modelcontextprotocol/server-filesystem" -- the actual server package name. npx downloads and runs this automatically.
• "/Users/yourname/Documents" -- the folder Claude is allowed to access. Replace this with a real path. You can add multiple folders as additional items in the args list.

Step 3: Save the file, then quit and relaunch Claude Desktop. The server starts automatically.

Step 4: Verify it is connected. In a conversation, look for the hammer icon in the input area -- this indicates MCP tools are available. Ask Claude: "What tools do you have available?" It will list the filesystem server and describe what it can do.

Popular MCP servers for business use

Anthropic and the broader community maintain servers for hundreds of services. Useful starting points:

• modelcontextprotocol.io -- official server list and SDK documentation
• claude.com/connectors -- Anthropic's verified connector directory (75+ services as of early 2026)
• GitHub search: mcp-server-[service-name] -- large community ecosystem covering Slack, GitHub, Airtable, HubSpot, Stripe, and thousands more

After editing the config

1. Save the file
2. Quit and relaunch Claude Desktop
3. In a conversation, look for the hammer icon in the input area -- this indicates MCP tools are available
4. Click the icon to see which servers are connected and what tools they expose
5. Ask Claude: "What tools do you have available?" -- it will list them by server

Troubleshooting

• No hammer icon after restart -- the config file has a JSON syntax error. A single missing comma will break the entire file. Paste the file contents into jsonlint.com to find the exact line with the problem.
• Hammer icon appears but server is missing -- the server failed to start. Check that Node.js is installed by opening a terminal and running node --version. If it is not found, download it from nodejs.org.
• Server not connecting to the external service -- an API token or credential is wrong, expired, or missing. Check the server's documentation for how to generate a fresh token.
• File path errors on macOS -- paths must be absolute (starting with /Users/yourname/), not relative. The shorthand ~/Documents may not work in the config file -- write the full path.
• macOS log: ~/Library/Logs/Claude/mcp.log -- if you cannot diagnose the problem from the above, open this file in a text editor to see the raw error messages from the server startup process.
• Test manually: copy the command from your config and run it directly in a terminal window to see its output. This is the fastest way to diagnose startup failures.