CursorMCPMonitor 0.1.0

Cursor MCP Monitor

A .NET console application that monitors Model Context Protocol (MCP) interactions in the Cursor AI editor. This tool helps developers debug and analyze MCP server-client communications by monitoring log files in real-time.

What is MCP?

The Model Context Protocol (MCP) is an open protocol that standardizes how applications provide context to LLMs. It follows a client-server architecture where:

• MCP Hosts (like Cursor) connect to multiple servers
• MCP Clients maintain 1:1 connections with servers
• MCP Servers expose specific capabilities through the standardized protocol
• Local Data Sources and Remote Services are accessed securely through MCP servers

Features

• Real-time monitoring of MCP client-server interactions in Cursor:
  • Client creation and connection events
  • Server offering listings and capabilities
  • Protocol errors and warnings
  • Client lifecycle transitions
• Monitors the Cursor logs directory for new MCP log files
• Parses and color-codes different message types:
  • Green: Client creation and successful connections
  • Yellow: Server offering listings
  • Red: Protocol errors and client closures
  • Gray: General information messages
• Supports log rotation and file truncation
• Cross-platform support (Windows, macOS, Linux)
• Smart error handling with exponential backoff and retry logic
• Configurable polling interval and log file patterns
• Command-line interface for easy customization
• Structured logging with Serilog for improved observability:
  • Console logging with formatted output
  • File logging with daily rotation
  • Contextual properties (machine name, thread ID, etc.)
  • Log level filtering and output customization

Installation

You can install the tool globally using the .NET CLI:

# Install from NuGet.org
dotnet tool install --global CursorMCPMonitor

# Or install from GitHub Packages
dotnet nuget add source --name github "https://nuget.pkg.github.com/willibrandon/index.json"
dotnet tool install --global CursorMCPMonitor --add-source github

After installation, you can run the tool from anywhere using:

cursor-mcp --help

To update to the latest version:

dotnet tool update --global CursorMCPMonitor

To uninstall:

dotnet tool uninstall --global CursorMCPMonitor

Configuration

The application can be configured through appsettings.json:

{
  "LogsRoot": null,
  "PollIntervalMs": 1000,
  "LogPattern": "Cursor MCP.log",
  "Verbosity": "Debug",
  "Filter": null,
  "Serilog": {
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft": "Warning",
        "System": "Warning"
      }
    },
    "Enrich": [ "FromLogContext", "WithMachineName", "WithThreadId" ],
    "Properties": {
      "Application": "CursorMCPMonitor"
    }
  },
  "Logging": {
    "LogLevel": {
      "Default": "Debug",
      "Microsoft": "Warning"
    }
  }
}

• LogsRoot: The root directory to monitor for Cursor MCP logs. If null, defaults to:
  • Windows: %AppData%/Cursor/logs
  • macOS: ~/Library/Application Support/Cursor/logs
  • Linux: ~/.config/Cursor/logs
• PollIntervalMs: How often to check for new log lines (in milliseconds)
• LogPattern: The log file pattern to monitor (supports glob patterns like "Cursor MCP*.log")
• Verbosity: The verbosity level (Debug, Information, Warning, Error). Defaults to Debug to show all messages.
• Filter: Optional text pattern to filter log content (only lines containing this text will be displayed)
• Serilog: Configuration for structured logging (see Serilog configuration)

You can also override settings using environment variables:

# Windows
set LogsRoot=C:\CustomPath\Cursor\logs
set PollIntervalMs=500
# Linux/macOS
export LogsRoot=/custom/path/cursor/logs
export PollIntervalMs=500

Serilog Configuration

The application uses Serilog for structured logging, which can be configured in the appsettings.json file:

• Serilog:MinimumLevel:Default: The default minimum log level
• Serilog:MinimumLevel:Override: Override minimum log levels for specific namespaces
• Serilog:Enrich: Enrichers to add contextual information to logs
• Serilog:Properties: Custom properties to include in all log events

By default, logs are written to:

• Console: Formatted for human readability
• Files: Stored in the logs directory with daily rotation as cursormonitor-YYYYMMDD.log

Command-Line Options

You can override configuration settings using command-line options:

# Specify a custom logs directory
dotnet run -- --logs-root "C:\Users\username\AppData\Roaming\Cursor\logs"

# Set a custom polling interval (500ms)
dotnet run -- --poll-interval 500

# Use a different log pattern (glob pattern support)
dotnet run -- --log-pattern "Cursor MCP*.log"

# Set verbosity level
dotnet run -- --verbosity debug

# Filter logs to only show lines containing specific text
dotnet run -- --filter "CreateClient"

# Combine multiple options
dotnet run -- --logs-root "/path/to/logs" --poll-interval 500 --verbosity error --filter "Error in MCP"

Building and Running

Prerequisites

• .NET 9.0 SDK or later

Build

dotnet build

Run

dotnet run

Docker Support

The application includes Docker support. To build and run using Docker:

# Make sure you're in the repository root directory
cd /path/to/CursorMCPMonitor

# Build the image (note the -f flag to specify Dockerfile location)
docker build -t cursor-mcp-monitor -f src/CursorMCPMonitor/Dockerfile .

# Run the container with volume mapping for logs
# For Windows PowerShell:
docker run -it --rm -v "$env:APPDATA\Cursor\logs:/app/logs" -e LogsRoot=/app/logs cursor-mcp-monitor

# For Windows CMD:
docker run -it --rm -v "%APPDATA%\Cursor\logs:/app/logs" -e LogsRoot=/app/logs cursor-mcp-monitor

# For macOS/Linux:
docker run -it --rm -v "$HOME/Library/Application Support/Cursor/logs:/app/logs" -e LogsRoot=/app/logs cursor-mcp-monitor

Important:

• Always run the Docker build command from the repository root directory, not from the project directory. This ensures that all necessary files are included in the build context.
• When running the Docker container, you need to map your local Cursor logs directory into the container and set the LogsRoot environment variable to point to the mapped directory.

Logging and Observability

The application implements structured logging using Serilog, which provides several benefits:

• Contextual Information: Each log entry includes contextual properties like machine name, thread ID, and source context
• Multiple Output Formats: Logs are written to both console and files in formatted output
• Log Levels: Different log levels (Debug, Information, Warning, Error, Fatal) help filter the most relevant information
• Structured Data: Log events include structured data that can be queried and analyzed
• Log Files: Log files are stored in the application's logs directory with daily rotation

Example log format (console):

[2025-03-03 12:34:56.789] [INF] [CursorMCPMonitor.Services.LogProcessorService] CreateClient detected: Cursor MCP.log 2025-03-03 12:34:56.123 [info] a602: Handling CreateClient action

Example log format (file):

2025-03-03 12:34:56.789 +00:00 [INF] [CursorMCPMonitor.Services.LogProcessorService] CreateClient detected: Cursor MCP.log 2025-03-03 12:34:56.123 [info] a602: Handling CreateClient action

Error Handling

The application includes advanced error handling:

• Exponential backoff with jitter for file access errors
• Automatic recovery from transient issues
• Detailed error reporting with color-coded console output
• File rotation and truncation detection
• Structured error logging with contextual information

Use Cases

• Debug MCP server implementations by monitoring client-server interactions
• Analyze protocol messages and error patterns
• Track client lifecycle and connection states
• Monitor server capabilities and offerings
• Verify correct protocol implementation
• Track application performance and error rates through structured logs

License

This project is licensed under the MIT License - see the LICENSE.txt file for details.