DotNet MCP Server Demo

using MCPDemo.Models; namespace MCPDemo.Services { public interface IMcpServer { Task<McpMessage> HandleMessageAsync(McpMessage message); Task<List<McpTool>> GetToolsAsync(); Task<List<McpResource>> GetResourcesAsync(); } public class McpServer : IMcpServer { private readonly ILogger<McpServer> _logger; private bool _initialized = false; public McpServer(ILogger<McpServer> logger) { _logger = logger; } public async Task<McpMessage> HandleMessageAsync(McpMessage message) { _logger.LogInformation($"Handling MCP message: {message.Method}"); try { return message.Method switch { "initialize" => await HandleInitializeAsync(message), "initialized" => HandleInitialized(message), "tools/list" => await HandleToolsListAsync(message), "tools/call" => await HandleToolCallAsync(message), "resources/list" => await HandleResourcesListAsync(message), "resources/read" => await HandleResourceReadAsync(message), _ => CreateErrorResponse(message.Id, -32601, "Method not found") }; } catch (Exception ex) { _logger.LogError(ex, "Error handling MCP message"); return CreateErrorResponse(message.Id, -32603, "Internal error"); } } private Task<McpMessage> HandleInitializeAsync(McpMessage message) { var serverInfo = new McpServerInfo { Name = "MCP Demo Server", Version = "1.0.0", ProtocolVersion = "2024-11-05", Capabilities = new McpCapabilities { Tools = new McpToolCapabilities { ListChanged = false }, Resources = new McpResourceCapabilities { Subscribe = false, ListChanged = false } } }; return Task.FromResult(new McpMessage { Id = message.Id, Result = serverInfo }); } private McpMessage HandleInitialized(McpMessage message) { _initialized = true; _logger.LogInformation("MCP Server initialized"); // No response needed for initialized notification return new McpMessage { Id = message.Id, Result = new { } }; } private async Task<McpMessage> HandleToolsListAsync(McpMessage message) { var tools = await GetToolsAsync(); return new McpMessage { Id = message.Id, Result = new { tools } }; } private async Task<McpMessage> HandleToolCallAsync(McpMessage message) { // Extract tool call from params var toolCall = System.Text.Json.JsonSerializer.Deserialize<McpToolCall>( System.Text.Json.JsonSerializer.Serialize(message.Params)); if (toolCall == null) { return CreateErrorResponse(message.Id, -32602, "Invalid tool call parameters"); } var result = await ExecuteToolAsync(toolCall); return new McpMessage { Id = message.Id, Result = result }; } private async Task<McpMessage> HandleResourcesListAsync(McpMessage message) { var resources = await GetResourcesAsync(); return new McpMessage { Id = message.Id, Result = new { resources } }; } private Task<McpMessage> HandleResourceReadAsync(McpMessage message) { // This is a simplified implementation return Task.FromResult(new McpMessage { Id = message.Id, Result = new { contents = new[] { new McpContent { Type = "text", Text = "Sample resource content" } } } }); } public Task<List<McpTool>> GetToolsAsync() { return Task.FromResult(new List<McpTool> { new McpTool { Name = "get_time", Description = "Get the current time", InputSchema = new { type = "object", properties = new { }, required = new string[] { } } }, new McpTool { Name = "echo", Description = "Echo back the provided message", InputSchema = new { type = "object", properties = new { message = new { type = "string", description = "The message to echo back" } }, required = new[] { "message" } } }, new McpTool { Name = "calculate", Description = "Perform basic arithmetic calculations", InputSchema = new { type = "object", properties = new { operation = new { type = "string", description = "The operation to perform (add, subtract, multiply, divide)", @enum = new[] { "add", "subtract", "multiply", "divide" } }, a = new { type = "number", description = "First number" }, b = new { type = "number", description = "Second number" } }, required = new[] { "operation", "a", "b" } } } }); } public Task<List<McpResource>> GetResourcesAsync() { return Task.FromResult(new List<McpResource> { new McpResource { Uri = "demo://sample-data", Name = "Sample Data", Description = "Sample data resource for demonstration", MimeType = "text/plain" } }); } private async Task<McpToolResult> ExecuteToolAsync(McpToolCall toolCall) { try { return toolCall.Name switch { "get_time" => new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = $"Current time: {DateTime.Now:yyyy-MM-dd HH:mm:ss}" } } }, "echo" => new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = toolCall.Arguments.ContainsKey("message") ? toolCall.Arguments["message"].ToString() ?? "No message provided" : "No message provided" } } }, "calculate" => await ExecuteCalculateToolAsync(toolCall.Arguments), _ => new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = $"Unknown tool: {toolCall.Name}" } }, IsError = true } }; } catch (Exception ex) { return new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = $"Error executing tool: {ex.Message}" } }, IsError = true }; } } private Task<McpToolResult> ExecuteCalculateToolAsync(Dictionary<string, object> arguments) { try { var operation = arguments["operation"].ToString(); var a = Convert.ToDouble(arguments["a"]); var b = Convert.ToDouble(arguments["b"]); double result = operation switch { "add" => a + b, "subtract" => a - b, "multiply" => a * b, "divide" => b != 0 ? a / b : throw new DivideByZeroException("Cannot divide by zero"), _ => throw new ArgumentException($"Unknown operation: {operation}") }; return Task.FromResult(new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = $"{a} {operation} {b} = {result}" } } }); } catch (Exception ex) { return Task.FromResult(new McpToolResult { Content = new List<McpContent> { new McpContent { Type = "text", Text = $"Calculation error: {ex.Message}" } }, IsError = true }); } } private McpMessage CreateErrorResponse(string? id, int code, string message) { return new McpMessage { Id = id, Error = new McpError { Code = code, Message = message } }; } } }