Make client config optional to McpClientFactory.CreateAsync (#65)

* Make client config optional to McpClientFactory.CreateAsync

Unless you're specifying capabilities (sampling/rooting) or need a specific client name/version, the client information can be inferred from the assembly, simplifying the getting-started experience.

* Cache default options

* Update src/ModelContextProtocol/Client/McpClientFactory.cs

Co-authored-by: Eirik Tsarpalis <[email protected]>

---------

Co-authored-by: Eirik Tsarpalis <[email protected]>

Author: stephentoub

README.MD

@@ -20,16 +20,10 @@ For more information about MCP:
 ## Getting Started (Client)
 
 To get started writing a client, the `McpClientFactory.CreateAsync` method is used to instantiate and connect an `IMcpClient`
-to a server, with details about the client and server specified in `McpClientOptions` and `McpServerConfig` objects.
-Once you have an `IMcpClient`, you can interact with it, such as to enumerate all available tools and invoke tools.
+to a server. Once you have an `IMcpClient`, you can interact with it, such as to enumerate all available tools and invoke tools.
 
 ```csharp
-McpClientOptions options = new()
-{
-    ClientInfo = new() { Name = "TestClient", Version = "1.0.0" }
-};
-
-McpServerConfig config = new()
+var client = await McpClientFactory.CreateAsync(new()
 {
     Id = "everything",
     Name = "Everything",
@@ -39,9 +33,7 @@ McpServerConfig config = new()
         ["command"] = "npx",
         ["arguments"] = "-y @modelcontextprotocol/server-everything",
     }
-};
-
-var client = await McpClientFactory.CreateAsync(config, options);
+});
 
 // Print the list of tools available from the server.
 await foreach (var tool in client.ListToolsAsync())

samples/ChatWithTools/Program.cs

@@ -15,8 +15,7 @@
         {
             ["command"] = "npx", ["arguments"] = "-y @modelcontextprotocol/server-everything",
         }
-    },
-    new() { ClientInfo = new() { Name = "ChatClient", Version = "1.0.0" } });
+    });
 
 // Get all available tools
 Console.WriteLine("Tools available:");

src/ModelContextProtocol/Client/McpClientFactory.cs

@@ -6,15 +6,36 @@
 using ModelContextProtocol.Utils;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
+using System.Reflection;
 
 namespace ModelContextProtocol.Client;
 
 /// <summary>Provides factory methods for creating MCP clients.</summary>
 public static class McpClientFactory
 {
+    /// <summary>Default client options to use when none are supplied.</summary>
+    private static readonly McpClientOptions s_defaultClientOptions = CreateDefaultClientOptions();
+
+    /// <summary>Creates default client options to use when no options are supplied.</summary>
+    private static McpClientOptions CreateDefaultClientOptions()
+    {
+        var asmName = (Assembly.GetEntryAssembly() ?? Assembly.GetExecutingAssembly()).GetName();
+        return new()
+        {
+            ClientInfo = new()
+            {
+                Name = asmName.Name ?? "McpClient",
+                Version = asmName.Version?.ToString() ?? "1.0.0",
+            },
+        };
+    }
+
     /// <summary>Creates an <see cref="IMcpClient"/>, connecting it to the specified server.</summary>
     /// <param name="serverConfig">Configuration for the target server to which the client should connect.</param>
-    /// <param name="clientOptions">A client configuration object which specifies client capabilities and protocol version.</param>
+    /// <param name="clientOptions">
+    /// A client configuration object which specifies client capabilities and protocol version.
+    /// If <see langword="null"/>, details based on the current process will be employed.
+    /// </param>
     /// <param name="createTransportFunc">An optional factory method which returns transport implementations based on a server configuration.</param>
     /// <param name="loggerFactory">A logger factory for creating loggers for clients.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
@@ -25,14 +46,14 @@ public static class McpClientFactory
     /// <exception cref="InvalidOperationException"><paramref name="createTransportFunc"/> returns an invalid transport.</exception>
     public static async Task<IMcpClient> CreateAsync(
         McpServerConfig serverConfig,
-        McpClientOptions clientOptions,
+        McpClientOptions? clientOptions = null,
         Func<McpServerConfig, ILoggerFactory?, IClientTransport>? createTransportFunc = null,
         ILoggerFactory? loggerFactory = null,
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(serverConfig);
-        Throw.IfNull(clientOptions);
 
+        clientOptions ??= s_defaultClientOptions;
         createTransportFunc ??= CreateTransport;
 
         string endpointName = $"Client ({serverConfig.Id}: {serverConfig.Name})";

tests/ModelContextProtocol.Tests/Client/McpClientFactoryTests.cs

@@ -19,13 +19,6 @@ public async Task CreateAsync_WithInvalidArgs_Throws()
     {
         await Assert.ThrowsAsync<ArgumentNullException>("serverConfig", () => McpClientFactory.CreateAsync((McpServerConfig)null!, _defaultOptions, cancellationToken: TestContext.Current.CancellationToken));
 
-        await Assert.ThrowsAsync<ArgumentNullException>("clientOptions", () => McpClientFactory.CreateAsync(new McpServerConfig()
-            {
-                Name = "name",
-                Id = "id",
-                TransportType = TransportTypes.StdIo,
-            }, (McpClientOptions)null!, cancellationToken: TestContext.Current.CancellationToken));
-
         await Assert.ThrowsAsync<ArgumentException>("serverConfig", () => McpClientFactory.CreateAsync(new McpServerConfig()
             {
                 Name = "name",
@@ -41,6 +34,28 @@ await Assert.ThrowsAsync<InvalidOperationException>(() => McpClientFactory.Creat
             }, _defaultOptions, (_, __) => null!, cancellationToken: TestContext.Current.CancellationToken));
     }
 
+    [Fact]
+    public async Task CreateAsync_NullOptions_EntryAssemblyInferred()
+    {
+        // Arrange
+        var serverConfig = new McpServerConfig
+        {
+            Id = "test-server",
+            Name = "Test Server",
+            TransportType = TransportTypes.StdIo,
+            Location = "/path/to/server",
+        };
+
+        // Act
+        await using var client = await McpClientFactory.CreateAsync(
+            serverConfig,
+            null,
+            (_, __) => new NopTransport(),
+            cancellationToken: TestContext.Current.CancellationToken);
+
+        Assert.NotNull(client);
+    }
+
     [Fact]
     public async Task CreateAsync_WithValidStdioConfig_CreatesNewClient()
     {