Fix: MCP Connection Failed

Error Message:

"Failed to connect to MCP server" "Connection refused at localhost:3000" "Tool execution failed: network error"

The Cause

You are trying to use a local integration (like the Google Drive connector or a local database tool), but Claude cannot reach the local server running on your machine.

The Fix

1. Check if the Server is Running

MCP servers are separate programs. They don't start automatically with Claude.

• Open your terminal.
• Check if your MCP server is active (e.g., npm run start or python server.py).
• Ensure it is printing "Listening on port XXXX".

2. Verify Port Configuration

Claude needs to know exactly which port to talk to.

• Go to Cowork Settings -> Integrations.
• Check the URL. Is it http://localhost:3000?
• Make sure your server is actually on port 3000. If it's on 8080, update the setting.

3. Check for Firewall/VPN

Corporate VPNs or firewalls sometimes block localhost connections.

• Temporarily disable your VPN.
• Check if your firewall software (Little Snitch, etc.) is blocking the connection.

4. Restart the "Connectors" Service

Sometimes the internal bridge crashes.

1. Close Claude Cowork completely (Quit).
2. Restart the application.
3. Wait 30 seconds for background services to initialize.