ModelContextProtocol.NET MCP Server

Installation

To get started with ModelContextProtocol.NET, you'll need to install the required NuGet packages:

1. Install the server package:

dotnet add package ModelContextProtocol.NET.Server --prerelease

2. For hosting integration, add the server hosting package:

dotnet add package ModelContextProtocol.NET.Server.Hosting --prerelease

Basic Usage

There are two main approaches to implementing an MCP server with this library:

Without Hosting

// Create server info
var serverInfo = new Implementation { Name = "Your Server Name", Version = "1.0.0" };

// Configure and build server
var builder = new McpServerBuilder(serverInfo).AddStdioTransport();

// Add logging (required when using stdio transport)
builder.Services.AddLogging(/* configure your logging provider */);

// Add tool handlers
builder.Tools.AddHandler<YourToolHandler>();

// Add function-based tools
builder.Tools.AddFunction(
    name: "yourToolName",
    description: "Description of what your tool does",
    parameterTypeInfo: YourParameterTypeJsonContext.Default.YourParameterType,
    handler: (YourParameterType parameters, CancellationToken ct) => {
        // Your tool implementation
        return Task.FromResult(new YourReturnType { /* results */ });
    }
);

// Build and start the server
var server = builder.Build();
server.Start();
await Task.Delay(-1); // Wait indefinitely

With Hosting

var builder = Host.CreateApplicationBuilder();
builder.Services.AddMcpServer(
    new Implementation { Name = "Your Server Name", Version = "1.0.0" }, 
    mcp => {
        mcp.AddStdioTransport();
        
        // Add your tools
        mcp.Tools.AddHandler<YourToolHandler>();
        mcp.Tools.AddFunction(/* same as above */);
    }, 
    keepDefaultLogging: false // clear default console logging
);

// Build and run the host
var host = builder.Build();
await host.RunAsync();

Logging Configuration

Since the MCP server uses Standard I/O for communication with AI models, you can't use console-based logging. You'll need to configure a different logging provider:

// Using Serilog
builder.Services.AddLogging(logging => logging.AddSerilog(yourSerilogLogger));

// Using NLog
builder.Services.AddLogging(logging => logging.AddNLog());

Implementing Tools

Tools are the core functionality of an MCP server. There are two ways to implement them:

1. Function-based tools: Quick and simple for straightforward tools

builder.Tools.AddFunction(
    name: "calculate",
    description: "Performs basic arithmetic calculations",
    parameterTypeInfo: CalculatorJsonContext.Default.CalculationRequest,
    handler: (CalculationRequest request, CancellationToken ct) => {
        // Implement calculation logic
        return Task.FromResult(new CalculationResponse { Result = /* calculated value */ });
    }
);

2. Handler-based tools: Better for complex tools that need dependency injection

// Define your handler class
public class CalculatorHandler : IToolHandler
{
    private readonly ILogger<CalculatorHandler> _logger;
    
    public CalculatorHandler(ILogger<CalculatorHandler> logger)
    {
        _logger = logger;
    }
    
    public string Name => "calculate";
    public string Description => "Performs basic arithmetic calculations";
    
    public async Task<object> HandleAsync(JsonElement parameters, CancellationToken cancellationToken)
    {
        // Parse parameters and implement calculation logic
        // Return result
    }
}

// Register your handler
builder.Tools.AddHandler<CalculatorHandler>();

Example Implementation

For a complete working example, refer to the calculator demo included in the repository (src/ModelContextProtocol.NET.Demo.Calculator). This demo covers:

• Proper logging setup
• Tool handler implementation
• Request/response handling
• Error management

Advanced Features

The library is actively being developed with additional features coming soon:

• WebSocket support for alternative communication channels
• Resource management for handling files and other resources
• Prompt system for more sophisticated interactions

Check the project's GitHub repository for the latest updates and features.