MCP (Model Context Protocol) servers extend Claude's capabilities by giving it access to external tools and data sources. The filesystem server is the most common starting point — it lets Claude read and write files on your machine, scoped to specific directories you choose.

The config

Add this to your Claude Desktop config file:

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

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

Each path in the args array is a directory Claude can access. It cannot read or write outside these directories.

What it enables

With the filesystem server running, Claude can:

• Read files you reference in conversation without you pasting them
• Write files directly (drafts, configs, scripts)
• List directory contents to understand project structure
• Search across files in the allowed directories

Security: scope carefully

Every path you add is a directory Claude can read and modify. Principles:

• Add project directories, not your home directory. /Users/yourname/Projects is fine. /Users/yourname gives access to SSH keys, credentials, browser data.
• Don't add directories with secrets. Keep .env files, credential stores, and private keys outside the allowed paths.
• Start narrow, widen later. Begin with one project directory. Add more as you find the need.

Adding more servers

MCP servers are composable. Add multiple servers for different capabilities:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/Users/yourname/Projects"]
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_your_token_here"
      }
    }
  }
}

Troubleshooting

"Server not found" or nothing happens — Restart Claude Desktop after editing the config file. MCP servers are loaded at startup.

"Permission denied" — The paths in args must exist and be readable by your user. Check with ls -la /path/you/added.

Server crashes silently — Check the MCP server logs. On macOS: ~/Library/Logs/Claude/mcp*.log

Tips

• You don't need MCP for Claude Code (the CLI) — it already has filesystem access built in. MCP filesystem is for Claude Desktop (the chat app).
• If you're using Claude Code, look at Git Guardrails instead for controlling what Claude can do with your files.