Program.cs

using EverythingServer;
using EverythingServer.Prompts;
using EverythingServer.Resources;
using EverythingServer.Tools;
using Microsoft.Extensions.AI;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using ModelContextProtocol;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Server;
using OpenTelemetry;
using OpenTelemetry.Logs;
using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

var builder = Host.CreateApplicationBuilder(args);
builder.Logging.AddConsole(consoleLogOptions =>
{
    // Configure all logs to go to stderr
    consoleLogOptions.LogToStandardErrorThreshold = LogLevel.Trace;
});

HashSet<string> subscriptions = [];
var _minimumLoggingLevel = LoggingLevel.Debug;

builder.Services
    .AddMcpServer()
    .WithStdioServerTransport()
    .WithTools<AddTool>()
    .WithTools<AnnotatedMessageTool>()
    .WithTools<EchoTool>()
    .WithTools<LongRunningTool>()
    .WithTools<PrintEnvTool>()
    .WithTools<SampleLlmTool>()
    .WithTools<TinyImageTool>()
    .WithPrompts<ComplexPromptType>()
    .WithPrompts<SimplePromptType>()
    .WithResources<SimpleResourceType>()
    .WithSubscribeToResourcesHandler(async (ctx, ct) =>
    {
        var uri = ctx.Params?.Uri;

        if (uri is not null)
        {
            subscriptions.Add(uri);

            await ctx.Server.SampleAsync([
                new ChatMessage(ChatRole.System, "You are a helpful test server"),
                new ChatMessage(ChatRole.User, $"Resource {uri}, context: A new subscription was started"),
            ],
            options: new ChatOptions
            {
                MaxOutputTokens = 100,
                Temperature = 0.7f,
            },
            cancellationToken: ct);
        }

        return new EmptyResult();
    })
    .WithUnsubscribeFromResourcesHandler(async (ctx, ct) =>
    {
        var uri = ctx.Params?.Uri;
        if (uri is not null)
        {
            subscriptions.Remove(uri);
        }
        return new EmptyResult();
    })
    .WithCompleteHandler(async (ctx, ct) =>
    {
        var exampleCompletions = new Dictionary<string, IEnumerable<string>>
        {
            { "style", ["casual", "formal", "technical", "friendly"] },
            { "temperature", ["0", "0.5", "0.7", "1.0"] },
            { "resourceId", ["1", "2", "3", "4", "5"] }
        };

        if (ctx.Params is not { } @params)
        {
            throw new NotSupportedException($"Params are required.");
        }

        var @ref = @params.Ref;
        var argument = @params.Argument;

        if (@ref.Type == "ref/resource")
        {
            var resourceId = @ref.Uri?.Split("/").Last();

            if (resourceId is null)
            {
                return new CompleteResult();
            }

            var values = exampleCompletions["resourceId"].Where(id => id.StartsWith(argument.Value));

            return new CompleteResult
            {
                Completion = new Completion { Values = [.. values], HasMore = false, Total = values.Count() }
            };
        }

        if (@ref.Type == "ref/prompt")
        {
            if (!exampleCompletions.TryGetValue(argument.Name, out IEnumerable<string>? value))
            {
                throw new NotSupportedException($"Unknown argument name: {argument.Name}");
            }

            var values = value.Where(value => value.StartsWith(argument.Value));
            return new CompleteResult
            {
                Completion = new Completion { Values = [.. values], HasMore = false, Total = values.Count() }
            };
        }

        throw new NotSupportedException($"Unknown reference type: {@ref.Type}");
    })
    .WithSetLoggingLevelHandler(async (ctx, ct) =>
    {
        if (ctx.Params?.Level is null)
        {
            throw new McpException("Missing required argument 'level'", McpErrorCode.InvalidParams);
        }

        _minimumLoggingLevel = ctx.Params.Level;

        await ctx.Server.SendNotificationAsync("notifications/message", new
        {
            Level = "debug",
            Logger = "test-server",
            Data = $"Logging level set to {_minimumLoggingLevel}",
        }, cancellationToken: ct);

        return new EmptyResult();
    });

ResourceBuilder resource = ResourceBuilder.CreateDefault().AddService("everything-server");
builder.Services.AddOpenTelemetry()
    .WithTracing(b => b.AddSource("*").AddHttpClientInstrumentation().SetResourceBuilder(resource))
    .WithMetrics(b => b.AddMeter("*").AddHttpClientInstrumentation().SetResourceBuilder(resource))
    .WithLogging(b => b.SetResourceBuilder(resource))
    .UseOtlpExporter();

builder.Services.AddSingleton(subscriptions);
builder.Services.AddHostedService<SubscriptionMessageSender>();
builder.Services.AddHostedService<LoggingUpdateMessageSender>();

builder.Services.AddSingleton<Func<LoggingLevel>>(_ => () => _minimumLoggingLevel);

await builder.Build().RunAsync();