Filter IAreaSetups to namespaces / tools specified on start

core/Azure.Mcp.Core/tests/Azure.Mcp.Core.Tests/CommandTests.cs

@@ -13,6 +13,11 @@ namespace Azure.Mcp.Core.Tests;
 public class CommandTests(ITestOutputHelper output, TestProxyFixture testProxyFixture, LiveServerFixture liveServerFixture)
     : RecordedCommandTestsBase(output, testProxyFixture, liveServerFixture)
 {
+    public override string[] Tools => [
+        "group_list",
+        "subscription_list"
+    ];
+
     [Fact]
     public async Task Should_list_groups_by_subscription()
     {
@@ -33,7 +38,7 @@ public async Task Should_list_subscriptions()
     {
         var result = await CallToolAsync(
             "subscription_list",
-            new Dictionary<string, object?>());
+            []);
 
         var subscriptionsArray = result.AssertProperty("subscriptions");
         Assert.Equal(JsonValueKind.Array, subscriptionsArray.ValueKind);

core/Microsoft.Mcp.Core/src/Areas/Server/Commands/ServiceStartCommand.cs

@@ -50,19 +50,19 @@ namespace Microsoft.Mcp.Core.Areas.Server.Commands;
     ReadOnly = true)]
 public sealed class ServiceStartCommand : BaseCommand<ServiceStartOptions>
 {
-    private static readonly string[] StdioHostBuilderArgs =
+    private static readonly string[] s_stdioHostBuilderArgs =
     [
         $"--contentRoot={AppContext.BaseDirectory}",
         "--hostBuilder:reloadConfigOnChange=false"
     ];
 
-    private static readonly WebApplicationOptions HttpWebApplicationOptions = new()
+    private static readonly WebApplicationOptions s_httpWebApplicationOptions = new()
     {
         ContentRootPath = AppContext.BaseDirectory
     };
 
+    public static List<IAreaSetup> Areas { get; set; } = [];
     public static Action<IServiceCollection> ConfigureServices { get; set; } = _ => { };
-
     public static Func<IServiceProvider, Task> InitializeServicesAsync { get; set; } = _ => Task.CompletedTask;
 
     /// <summary>
@@ -186,6 +186,23 @@ public override async Task<CommandResponse> ExecuteAsync(CommandContext context,
 
         try
         {
+            // After binding options, see if any tool filters were applied (--namespace or --tool).
+            // If any were specified, filter Areas based on the IAreaSetup name (case-insensitive).
+            var hasNamespace = options.Namespace is { Length: > 0 };
+            var hasTool = options.Tool is { Length: > 0 };
+            if (hasNamespace || hasTool)
+            {
+                // --namespace and --tool are mutually exclusive. Setup the filter based on which was set.
+                // When --namespace is used, use the namespace as the filter, as that should already be the IAreaSetup name.
+                // When --tool is used, use the first part of each tool name (split by '_') as the filter, as that represents the area (e.g., 'storage_account_get' -> 'storage').
+                var areaNames = hasNamespace ?
+                    new HashSet<string>(options.Namespace!, StringComparer.OrdinalIgnoreCase)! :
+                    options.Tool?.Select(t => t.Split('_').First()).ToHashSet(StringComparer.OrdinalIgnoreCase)!;
+
+                // Filter the Areas that were setup by Program.cs.
+                Areas.RemoveAll(area => !areaNames.Contains(area.Name));
+            }
+
             using var tracerProvider = AddIncomingAndOutgoingHttpSpans(options);
 
             using var host = CreateHost(options);
@@ -403,7 +420,7 @@ private IHost CreateHost(ServiceStartOptions serverOptions)
     /// <returns>An IHost instance configured for STDIO transport.</returns>
     private IHost CreateStdioHost(ServiceStartOptions serverOptions)
     {
-        return Host.CreateDefaultBuilder(StdioHostBuilderArgs)
+        return Host.CreateDefaultBuilder(s_stdioHostBuilderArgs)
             .ConfigureLogging(logging =>
             {
                 logging.ClearProviders();
@@ -453,7 +470,7 @@ private IHost CreateStdioHost(ServiceStartOptions serverOptions)
     /// <returns>An IHost instance configured for HTTP transport.</returns>
     private IHost CreateHttpHost(ServiceStartOptions serverOptions)
     {
-        WebApplicationBuilder builder = WebApplication.CreateBuilder(HttpWebApplicationOptions);
+        WebApplicationBuilder builder = WebApplication.CreateBuilder(s_httpWebApplicationOptions);
 
         // Read once at host setup time — this env var is process-wide and effectively static,
         // so there is no need to re-read it on every incoming request.
@@ -645,7 +662,7 @@ await JsonSerializer.SerializeAsync(
     /// <returns>An IHost instance configured for HTTP transport.</returns>
     private IHost CreateIncomingAuthDisabledHttpHost(ServiceStartOptions serverOptions)
     {
-        WebApplicationBuilder builder = WebApplication.CreateBuilder(HttpWebApplicationOptions);
+        WebApplicationBuilder builder = WebApplication.CreateBuilder(s_httpWebApplicationOptions);
 
         InitializeListingUrls(builder, serverOptions);
 

core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/CommandTestsBase.cs

@@ -24,17 +24,16 @@ public abstract class CommandTestsBase(ITestOutputHelper output, LiveServerFixtu
     protected ITestOutputHelper Output { get; } = output;
     protected LiveServerFixture LiveServerFixture { get; } = liveServerFixture;
 
-    public string[]? CustomArguments;
     public TestMode TestMode = TestMode.Live;
 
     /// <summary>
-    /// Sets custom arguments for the MCP server. Call this before InitializeAsync().
+    /// Sets the tools that the MCP server will scope to. Call this before InitializeAsync().
+    /// <para>
+    /// This reduces the number of tools that the MCP server will load and initialize.
+    /// </para>
     /// </summary>
-    /// <param name="arguments">Custom arguments to pass to the server (e.g., ["server", "start", "--mode", "single"])</param>
-    public void SetArguments(params string[] arguments)
-    {
-        CustomArguments = arguments;
-    }
+    /// <param name="tools">Tools to pass to the server (e.g., "storage_blob_get", "appconfig_kv_get", etc.)</param>
+    public virtual string[] Tools => [];
 
     public virtual async ValueTask InitializeAsync()
     {
@@ -124,10 +123,21 @@ protected virtual async ValueTask InitializeAsyncInternal(TestProxyFixture? prox
         // Use custom arguments if provided, otherwise use standard mode (debug can be enabled via environment variable)
         var debugEnvVar = Environment.GetEnvironmentVariable("AZURE_MCP_TEST_DEBUG");
         var enableDebug = string.Equals(debugEnvVar, "true", StringComparison.OrdinalIgnoreCase) || Settings.DebugOutput;
-        List<string> defaultArgs = enableDebug
+
+        // Live testing uses '--mode all' as it doesn't require sampling and the way live tests are ran an agent isn't
+        // used to make the request, so sampling isn't available.
+        List<string> arguments = enableDebug
             ? ["server", "start", "--mode", "all", "--debug", "--dangerously-disable-elicitation", "--disable-caching"]
             : ["server", "start", "--mode", "all", "--dangerously-disable-elicitation", "--disable-caching"];
-        var arguments = CustomArguments?.ToList() ?? defaultArgs;
+
+        if (Tools != null && Tools.Length > 0)
+        {
+            foreach (var tool in Tools)
+            {
+                arguments.Add("--tool");
+                arguments.Add(tool);
+            }
+        }
 
         LiveServerFixture.EnvironmentVariables = GetEnvironmentVariables(proxy);
         LiveServerFixture.Arguments = arguments;

core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/Helpers/McpTestUtilities.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System.Diagnostics;
+using System.Net;
 using System.Reflection;
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Protocol;
@@ -190,9 +191,9 @@ private static IClientTransport CreateStdioTransport(
     /// <returns>An available port number.</returns>
     private static int GetAvailablePort()
     {
-        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
+        using var listener = new System.Net.Sockets.TcpListener(IPAddress.Loopback, 0);
         listener.Start();
-        var port = ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
         listener.Stop();
         return port;
     }
@@ -261,24 +262,22 @@ public static async Task WaitForServerReadinessAsync(
                     id = Guid.NewGuid().ToString()
                 };
 
-                var content = new System.Net.Http.StringContent(
+                var content = new StringContent(
                     System.Text.Json.JsonSerializer.Serialize(request),
                     System.Text.Encoding.UTF8,
                     "application/json");
                 using var requestMessage = new HttpRequestMessage(HttpMethod.Post, serverUrl)
                 {
                     Content = content
                 };
-                requestMessage.Headers.Accept.Add(
-                    new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
-                requestMessage.Headers.Accept.Add(
-                    new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("text/event-stream"));
+                requestMessage.Headers.Accept.Add(new("application/json"));
+                requestMessage.Headers.Accept.Add(new("text/event-stream"));
                 using var resp = await httpClient.SendAsync(requestMessage);
 
                 // If authentication is enabled, 401 Unauthorized means server is ready
                 // If authentication is disabled, we need a success status code
                 if (resp.IsSuccessStatusCode || (authenticationEnabled &&
-                    (resp.StatusCode == System.Net.HttpStatusCode.Unauthorized || resp.StatusCode == System.Net.HttpStatusCode.Forbidden)))
+                    (resp.StatusCode == HttpStatusCode.Unauthorized || resp.StatusCode == HttpStatusCode.Forbidden)))
                 {
                     return;
                 }

core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/LiveServerFixture.cs

@@ -16,7 +16,7 @@ public sealed class LiveServerFixture() : IAsyncLifetime
     private string? _serverUrl;
     private bool _started;
 
-    public Dictionary<string, string?> EnvironmentVariables { get; set; } = new();
+    public Dictionary<string, string?> EnvironmentVariables { get; set; } = [];
     public List<string> Arguments { get; set; } = [];
     public ITestOutputHelper? Output { get; set; }
     public LiveTestSettings? Settings { get; set; }
@@ -60,11 +60,7 @@ public async Task EnsureStartedAsync()
 
     public McpClient GetMcpClient()
     {
-        if (_mcpClient == null)
-        {
-            throw new InvalidOperationException("MCP Client has not been initialized.");
-        }
-        return _mcpClient;
+        return _mcpClient ?? throw new InvalidOperationException("MCP Client has not been initialized.");
     }
 
     public async ValueTask DisposeAsync()

servers/Azure.Mcp.Server/src/Program.cs

@@ -7,7 +7,6 @@
 using Azure.Mcp.Core.Services.Azure.Subscription;
 using Azure.Mcp.Core.Services.Azure.Tenant;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
@@ -33,12 +32,11 @@ namespace Azure.Mcp.Server;
 
 internal class Program
 {
-    private static readonly IAreaSetup[] Areas = RegisterAreas();
+    private static readonly List<IAreaSetup> s_areas = RegisterAreas();
 
     // Derived from the registered ServerSetup instance so the name stays in sync
     // with the actual area registration — no magic string duplication.
-    private static readonly string ServerAreaName =
-        Array.Find(Areas, static a => a is Microsoft.Mcp.Core.Areas.Server.ServerSetup)?.Name ?? "server";
+    private static readonly string s_serverAreaName = s_areas.First(static a => a is ServerSetup)?.Name ?? "server";
 
     private static async Task<int> Main(string[] args)
     {
@@ -53,6 +51,7 @@ private static async Task<int> Main(string[] args)
             }
 
             // The server start and plugin-telemetry containers always need full area registration.
+            ServiceStartCommand.Areas = s_areas;
             ServiceStartCommand.ConfigureServices = services => ConfigureServices(services);
             ServiceStartCommand.InitializeServicesAsync = InitializeServicesAsync;
 
@@ -65,7 +64,7 @@ private static async Task<int> Main(string[] args)
 
             ServiceCollection services = new();
 
-            ConfigureServices(services, targetAreaName);
+            ConfigureServices(services, areaSetup => string.Equals(areaSetup.Name, targetAreaName, StringComparison.OrdinalIgnoreCase));
 
             services.AddLogging(builder =>
             {
@@ -169,17 +168,17 @@ private static async Task<int> Main(string[] args)
         }
     }
 
-    private static IAreaSetup[] RegisterAreas()
+    private static List<IAreaSetup> RegisterAreas()
     {
 
         return [
             // Register core areas
+            new Microsoft.Mcp.Core.Areas.Server.ServerSetup(),
+            new Microsoft.Mcp.Core.Areas.Tools.ToolsSetup(),
             new Azure.Mcp.Tools.AzureBestPractices.AzureBestPracticesSetup(),
             new Azure.Mcp.Tools.Extension.ExtensionSetup(),
             new Azure.Mcp.Core.Areas.Group.GroupSetup(),
-            new Microsoft.Mcp.Core.Areas.Server.ServerSetup(),
             new Azure.Mcp.Core.Areas.Subscription.SubscriptionSetup(),
-            new Microsoft.Mcp.Core.Areas.Tools.ToolsSetup(),
             // Register Azure service areas
             new Azure.Mcp.Tools.Aks.AksSetup(),
             new Azure.Mcp.Tools.AppConfig.AppConfigSetup(),
@@ -311,7 +310,7 @@ private static void WriteResponse(CommandResponse response)
     /// (those with <see cref="CommandCategory"/> other than <see cref="CommandCategory.AzureServices"/>)
     /// have their services registered. Pass <see langword="null"/> for full initialization.
     /// </param>
-    internal static void ConfigureServices(IServiceCollection services, string? areaFilter = null)
+    internal static void ConfigureServices(IServiceCollection services, Predicate<IAreaSetup>? areaFilter = null)
     {
         var thisAssembly = typeof(Program).Assembly;
 
@@ -334,27 +333,27 @@ internal static void ConfigureServices(IServiceCollection services, string? area
         services.AddAzureTenantService();
         services.AddSingleUserCliCacheService(disabled: true);
 
-        foreach (var area in Areas)
+        bool configuredServerArea = false;
+        foreach (var area in s_areas)
         {
             // When areaFilter is set (CLI path), skip Azure service areas that don't match the target.
             // Non-Azure-service areas (Category != AzureServices) provide shared infrastructure
             // (command routing, server start, subscription listing, etc.) and must always be registered.
             // Any area whose Category is AzureServices and whose name doesn't match the filter is skipped;
             // this avoids registering services (HTTP clients, SDKs, etc.) for 60+ irrelevant services.
-            if (areaFilter != null &&
-                area.Category == CommandCategory.AzureServices &&
-                !string.Equals(area.Name, areaFilter, StringComparison.OrdinalIgnoreCase))
+            if (areaFilter != null && area.Category == CommandCategory.AzureServices && !areaFilter(area))
             {
                 continue;
             }
             services.AddSingleton(area);
             area.ConfigureServices(services);
+            configuredServerArea |= string.Equals(area.Name, s_serverAreaName, StringComparison.OrdinalIgnoreCase);
         }
 
         // Optimization: server-mode providers (registry, instructions, plugin allowlists) are only
         // used when running as an MCP server. For CLI area invocations they are never resolved, so
         // register lightweight stubs to avoid reading embedded resources on every CLI call.
-        if (areaFilter == null || string.Equals(areaFilter, ServerAreaName, StringComparison.OrdinalIgnoreCase))
+        if (areaFilter == null || configuredServerArea)
         {
             services.AddRegistryRoot(thisAssembly, $"registry.json");
 
@@ -443,7 +442,7 @@ internal static async Task InitializeServicesAsync(IServiceProvider serviceProvi
         // Only apply the optimization when the first token is a known registered area.
         // If the token doesn't match any area (e.g. a typo), fall through to full initialization
         // so System.CommandLine can produce helpful "Did you mean..." suggestions.
-        if (!Array.Exists(Areas, a => string.Equals(a.Name, firstToken, StringComparison.OrdinalIgnoreCase)))
+        if (!s_areas.Any(a => string.Equals(a.Name, firstToken, StringComparison.OrdinalIgnoreCase)))
         {
             return null;
         }

servers/Fabric.Mcp.Server/src/Program.cs

@@ -24,12 +24,13 @@
 
 internal class Program
 {
-    private static IAreaSetup[] Areas = RegisterAreas();
+    private static readonly List<IAreaSetup> s_areas = RegisterAreas();
 
     private static async Task<int> Main(string[] args)
     {
         try
         {
+            ServiceStartCommand.Areas = s_areas;
             ServiceStartCommand.ConfigureServices = ConfigureServices;
             ServiceStartCommand.InitializeServicesAsync = InitializeServicesAsync;
 
@@ -103,7 +104,7 @@ private static async Task<int> Main(string[] args)
             return 1;
         }
     }
-    private static IAreaSetup[] RegisterAreas()
+    private static List<IAreaSetup> RegisterAreas()
     {
 
         return [
@@ -191,7 +192,7 @@ internal static void ConfigureServices(IServiceCollection services)
         services.AddHttpClientServices();
         services.AddSingleUserCliCacheService(disabled: true);
 
-        foreach (var area in Areas)
+        foreach (var area in s_areas)
         {
             services.AddSingleton(area);
             area.ConfigureServices(services);