MCP Servers Cheatsheet

Configuration Format (.claude.exs)

%{
  mcp_servers: [
    # Simple format
    :tidewave,
    
    # With options
    {:tidewave, [port: 5000]},
    
    # Disabled
    {:tidewave, [enabled?: false]}
  ]
}

Server Options

Available Servers

Installation Flow

# Step 1: Configure in .claude.exs
# Step 2: Run install to sync
mix claude.install

# Creates/updates .mcp.json

Generated .mcp.json

{
  "mcpServers": {
    "tidewave": {
      "command": "npx",
      "args": ["-y", "@bradleygolden/mcp-server-tidewave"],
      "env": {
        "PORT": "4000"
      }
    }
  }
}

Phoenix Auto-Configuration

# Automatically added when Phoenix detected:
%{
  mcp_servers: [:tidewave]
}

Custom Port Configuration

# Development
{:tidewave, [port: 4000]}

# Staging  
{:tidewave, [port: 4001]}

# Local testing
{:tidewave, [port: 5000]}

Disable Without Removing

# Temporarily disable
{:tidewave, [enabled?: false]}

# Re-enable later
{:tidewave, [enabled?: true]}  # or just :tidewave

Manual .mcp.json

If you need custom MCP servers not managed by Claude:

{
  "mcpServers": {
    "custom-server": {
      "command": "node",
      "args": ["path/to/server.js"],
      "env": {
        "API_KEY": "secret"
      }
    }
  }
}

Troubleshooting

Port Defaults

Environment Variables

MCP servers receive these env vars:

# From .mcp.json
"env": {
  "PORT": "4000",           # Server port
  "PROJECT_DIR": "/path/to/project"
}

Development Setup

%{
  mcp_servers: [
    {:tidewave, [port: 4000]}  # Match Phoenix dev port
  ]
}

Multi-Environment

%{
  mcp_servers: [
    # Use environment variable
    {:tidewave, [port: System.get_env("MCP_PORT", "4000")]}
  ]
}

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