Remove McpServerConfig and have McpClientFactory accept IClientTransport instances directly. (#230)

* Remove McpServerConfig and have McpClientFactory accept IClientTransport instances directly.

* Address feedback and use lists when representing stdio arguments.

* Use "Name" for transport descriptors and "EndpointName" for MCP clients and servers.

* Update code samples.

* Fix source file naming

Author: eiriktsarpalis

README.md

@@ -31,18 +31,15 @@ To get started writing a client, the `McpClientFactory.CreateAsync` method is us
 to a server. Once you have an `IMcpClient`, you can interact with it, such as to enumerate all available tools and invoke tools.
 
 ```csharp
-var client = await McpClientFactory.CreateAsync(new()
+var clientTransport = new StdioClientTransport(new()
 {
-    Id = "everything",
     Name = "Everything",
-    TransportType = TransportTypes.StdIo,
-    TransportOptions = new()
-    {
-        ["command"] = "npx",
-        ["arguments"] = "-y @modelcontextprotocol/server-everything",
-    }
+    Command = "npx",
+    Arguments = ["-y", "@modelcontextprotocol/server-everything"],
 });
 
+var client = await McpClientFactory.CreateAsync(clientTransport);
+
 // Print the list of tools available from the server.
 foreach (var tool in await client.ListToolsAsync())
 {

samples/ChatWithTools/Program.cs

@@ -6,16 +6,12 @@
 // Connect to an MCP server
 Console.WriteLine("Connecting client to MCP 'everything' server");
 var mcpClient = await McpClientFactory.CreateAsync(
-    new()
+    new StdioClientTransport(new()
     {
-        Id = "everything",
+        Command = "npx",
+        Arguments = ["-y", "--verbose", "@modelcontextprotocol/server-everything"],
         Name = "Everything",
-        TransportType = TransportTypes.StdIo,
-        TransportOptions = new()
-        {
-            ["command"] = "npx", ["arguments"] = "-y @modelcontextprotocol/server-everything",
-        }
-    });
+    }));
 
 // Get all available tools
 Console.WriteLine("Tools available:");

samples/QuickstartClient/Program.cs

@@ -13,18 +13,15 @@
 
 var (command, arguments) = GetCommandAndArguments(args);
 
-await using var mcpClient = await McpClientFactory.CreateAsync(new()
+var clientTransport = new StdioClientTransport(new()
 {
-    Id = "demo-server",
     Name = "Demo Server",
-    TransportType = TransportTypes.StdIo,
-    TransportOptions = new()
-    {
-        ["command"] = command,
-        ["arguments"] = arguments,
-    }
+    Command = command,
+    Arguments = arguments,
 });
 
+await using var mcpClient = await McpClientFactory.CreateAsync(clientTransport);
+
 var tools = await mcpClient.ListToolsAsync();
 foreach (var tool in tools)
 {
@@ -86,13 +83,13 @@ static void PromptForInput()
 /// 
 /// This method would only be required if you're creating a generic client, such as we use for the quickstart.
 /// </remarks>
-static (string command, string arguments) GetCommandAndArguments(string[] args)
+static (string command, string[] arguments) GetCommandAndArguments(string[] args)
 {
     return args switch
     {
-        [var script] when script.EndsWith(".py") => ("python", script),
-        [var script] when script.EndsWith(".js") => ("node", script),
-        [var script] when Directory.Exists(script) || (File.Exists(script) && script.EndsWith(".csproj")) => ("dotnet", $"run --project {script} --no-build"),
-        _ => ("dotnet", "run --project ../../../../QuickstartWeatherServer --no-build")
+        [var script] when script.EndsWith(".py") => ("python", args),
+        [var script] when script.EndsWith(".js") => ("node", args),
+        [var script] when Directory.Exists(script) || (File.Exists(script) && script.EndsWith(".csproj")) => ("dotnet", ["run", "--project", script, "--no-build"]),
+        _ => ("dotnet", ["run", "--project", "../../../../QuickstartWeatherServer", "--no-build"])
     };
 }

src/Common/Polyfills/System/PasteArguments.cs

@@ -0,0 +1,101 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Copied from:
+// https://github.com/dotnet/runtime/blob/d2650b6ae7023a2d9d2c74c56116f1f18472ab04/src/libraries/System.Private.CoreLib/src/System/PasteArguments.cs
+// and changed from using ValueStringBuilder to StringBuilder.
+
+using System.Text;
+
+namespace System;
+
+internal static partial class PasteArguments
+{
+    internal static void AppendArgument(StringBuilder stringBuilder, string argument)
+    {
+        if (stringBuilder.Length != 0)
+        {
+            stringBuilder.Append(' ');
+        }
+
+        // Parsing rules for non-argv[0] arguments:
+        //   - Backslash is a normal character except followed by a quote.
+        //   - 2N backslashes followed by a quote ==> N literal backslashes followed by unescaped quote
+        //   - 2N+1 backslashes followed by a quote ==> N literal backslashes followed by a literal quote
+        //   - Parsing stops at first whitespace outside of quoted region.
+        //   - (post 2008 rule): A closing quote followed by another quote ==> literal quote, and parsing remains in quoting mode.
+        if (argument.Length != 0 && ContainsNoWhitespaceOrQuotes(argument))
+        {
+            // Simple case - no quoting or changes needed.
+            stringBuilder.Append(argument);
+        }
+        else
+        {
+            stringBuilder.Append(Quote);
+            int idx = 0;
+            while (idx < argument.Length)
+            {
+                char c = argument[idx++];
+                if (c == Backslash)
+                {
+                    int numBackSlash = 1;
+                    while (idx < argument.Length && argument[idx] == Backslash)
+                    {
+                        idx++;
+                        numBackSlash++;
+                    }
+
+                    if (idx == argument.Length)
+                    {
+                        // We'll emit an end quote after this so must double the number of backslashes.
+                        stringBuilder.Append(Backslash, numBackSlash * 2);
+                    }
+                    else if (argument[idx] == Quote)
+                    {
+                        // Backslashes will be followed by a quote. Must double the number of backslashes.
+                        stringBuilder.Append(Backslash, numBackSlash * 2 + 1);
+                        stringBuilder.Append(Quote);
+                        idx++;
+                    }
+                    else
+                    {
+                        // Backslash will not be followed by a quote, so emit as normal characters.
+                        stringBuilder.Append(Backslash, numBackSlash);
+                    }
+
+                    continue;
+                }
+
+                if (c == Quote)
+                {
+                    // Escape the quote so it appears as a literal. This also guarantees that we won't end up generating a closing quote followed
+                    // by another quote (which parses differently pre-2008 vs. post-2008.)
+                    stringBuilder.Append(Backslash);
+                    stringBuilder.Append(Quote);
+                    continue;
+                }
+
+                stringBuilder.Append(c);
+            }
+
+            stringBuilder.Append(Quote);
+        }
+    }
+
+    private static bool ContainsNoWhitespaceOrQuotes(string s)
+    {
+        for (int i = 0; i < s.Length; i++)
+        {
+            char c = s[i];
+            if (char.IsWhiteSpace(c) || c == Quote)
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    private const char Quote = '\"';
+    private const char Backslash = '\\';
+}

src/ModelContextProtocol/Client/McpClient.cs

@@ -33,17 +33,16 @@ internal sealed class McpClient : McpEndpoint, IMcpClient
     /// </summary>
     /// <param name="clientTransport">The transport to use for communication with the server.</param>
     /// <param name="options">Options for the client, defining protocol version and capabilities.</param>
-    /// <param name="serverConfig">The server configuration.</param>
     /// <param name="loggerFactory">The logger factory.</param>
-    public McpClient(IClientTransport clientTransport, McpClientOptions? options, McpServerConfig serverConfig, ILoggerFactory? loggerFactory)
+    public McpClient(IClientTransport clientTransport, McpClientOptions? options, ILoggerFactory? loggerFactory)
         : base(loggerFactory)
     {
         options ??= new();
 
         _clientTransport = clientTransport;
         _options = options;
 
-        EndpointName = $"Client ({serverConfig.Id}: {serverConfig.Name})";
+        EndpointName = clientTransport.Name;
 
         if (options.Capabilities is { } capabilities)
         {

src/ModelContextProtocol/Client/McpClientFactory.cs

@@ -12,128 +12,39 @@ namespace ModelContextProtocol.Client;
 public static class McpClientFactory
 {
     /// <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="clientTransport">The transport instance used to communicate with the server.</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">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>An <see cref="IMcpClient"/> that's connected to the specified server.</returns>
-    /// <exception cref="ArgumentNullException"><paramref name="serverConfig"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException"><paramref name="clientTransport"/> is <see langword="null"/>.</exception>
     /// <exception cref="ArgumentNullException"><paramref name="clientOptions"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException"><paramref name="serverConfig"/> contains invalid information.</exception>
-    /// <exception cref="InvalidOperationException"><paramref name="createTransportFunc"/> returns an invalid transport.</exception>
     public static async Task<IMcpClient> CreateAsync(
-        McpServerConfig serverConfig,
+        IClientTransport clientTransport,
         McpClientOptions? clientOptions = null,
-        Func<McpServerConfig, ILoggerFactory?, IClientTransport>? createTransportFunc = null,
         ILoggerFactory? loggerFactory = null,
         CancellationToken cancellationToken = default)
     {
-        Throw.IfNull(serverConfig);
-
-        createTransportFunc ??= CreateTransport;
-        
-        string endpointName = $"Client ({serverConfig.Id}: {serverConfig.Name})";
+        Throw.IfNull(clientTransport);
 
+        string endpointName = clientTransport.Name;
         var logger = loggerFactory?.CreateLogger(typeof(McpClientFactory)) ?? NullLogger.Instance;
         logger.CreatingClient(endpointName);
 
-        var transport = 
-            createTransportFunc(serverConfig, loggerFactory) ??
-            throw new InvalidOperationException($"{nameof(createTransportFunc)} returned a null transport.");
-
+        McpClient client = new(clientTransport, clientOptions, loggerFactory);
         try
         {
-            McpClient client = new(transport, clientOptions, serverConfig, loggerFactory);
-            try
-            {
-                await client.ConnectAsync(cancellationToken).ConfigureAwait(false);
-                logger.ClientCreated(endpointName);
-                return client;
-            }
-            catch
-            {
-                await client.DisposeAsync().ConfigureAwait(false);
-                throw;
-            }
+            await client.ConnectAsync(cancellationToken).ConfigureAwait(false);
+            logger.ClientCreated(endpointName);
+            return client;
         }
         catch
         {
-            if (transport is IAsyncDisposable asyncDisposableTransport)
-            {
-                await asyncDisposableTransport.DisposeAsync().ConfigureAwait(false);
-            }
-            else if (transport is IDisposable disposableTransport)
-            {
-                disposableTransport.Dispose();
-            }
+            await client.DisposeAsync().ConfigureAwait(false);
             throw;
         }
     }
-
-    private static IClientTransport CreateTransport(McpServerConfig serverConfig, ILoggerFactory? loggerFactory)
-    {
-        if (string.Equals(serverConfig.TransportType, TransportTypes.StdIo, StringComparison.OrdinalIgnoreCase))
-        {
-            string? command = serverConfig.TransportOptions?.GetValueOrDefault("command");
-            if (string.IsNullOrWhiteSpace(command))
-            {
-                command = serverConfig.Location;
-                if (string.IsNullOrWhiteSpace(command))
-                {
-                    throw new ArgumentException("Command is required for stdio transport.", nameof(serverConfig));
-                }
-            }
-
-            string? arguments = serverConfig.TransportOptions?.GetValueOrDefault("arguments");
-
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) &&
-                serverConfig.TransportType.Equals(TransportTypes.StdIo, StringComparison.OrdinalIgnoreCase) &&
-                !string.IsNullOrEmpty(command) &&
-                !string.Equals(Path.GetFileName(command), "cmd.exe", StringComparison.OrdinalIgnoreCase))
-            {
-                // On Windows, for stdio, we need to wrap non-shell commands with cmd.exe /c {command} (usually npx or uvicorn).
-                // The stdio transport will not work correctly if the command is not run in a shell.
-                arguments = string.IsNullOrWhiteSpace(arguments) ? 
-                    $"/c {command}" :
-                    $"/c {command} {arguments}";
-                command = "cmd.exe";
-            }
-
-            return new StdioClientTransport(new StdioClientTransportOptions
-            {
-                Command = command!,
-                Arguments = arguments,
-                WorkingDirectory = serverConfig.TransportOptions?.GetValueOrDefault("workingDirectory"),
-                EnvironmentVariables = serverConfig.TransportOptions?
-                    .Where(kv => kv.Key.StartsWith("env:", StringComparison.Ordinal))
-                    .ToDictionary(kv => kv.Key.Substring("env:".Length), kv => kv.Value),
-                ShutdownTimeout = TimeSpan.TryParse(serverConfig.TransportOptions?.GetValueOrDefault("shutdownTimeout"), CultureInfo.InvariantCulture, out var timespan) ? timespan : StdioClientTransportOptions.DefaultShutdownTimeout
-            }, serverConfig, loggerFactory);
-        }
-
-        if (string.Equals(serverConfig.TransportType, TransportTypes.Sse, StringComparison.OrdinalIgnoreCase) ||
-            string.Equals(serverConfig.TransportType, "http", StringComparison.OrdinalIgnoreCase))
-        {
-            return new SseClientTransport(new SseClientTransportOptions
-            {
-                ConnectionTimeout = TimeSpan.FromSeconds(ParseInt32OrDefault(serverConfig.TransportOptions, "connectionTimeout", 30)),
-                MaxReconnectAttempts = ParseInt32OrDefault(serverConfig.TransportOptions, "maxReconnectAttempts", 3),
-                ReconnectDelay = TimeSpan.FromSeconds(ParseInt32OrDefault(serverConfig.TransportOptions, "reconnectDelay", 5)),
-                AdditionalHeaders = serverConfig.TransportOptions?
-                    .Where(kv => kv.Key.StartsWith("header.", StringComparison.Ordinal))
-                    .ToDictionary(kv => kv.Key.Substring("header.".Length), kv => kv.Value)
-            }, serverConfig, loggerFactory);
-
-            static int ParseInt32OrDefault(Dictionary<string, string>? options, string key, int defaultValue) =>
-                options?.TryGetValue(key, out var value) is not true ? defaultValue :
-                int.TryParse(value, out var result) ? result :
-                throw new ArgumentException($"Invalid value '{value}' for option '{key}' in transport options.", nameof(serverConfig));
-        }
-
-        throw new ArgumentException($"Unsupported transport type '{serverConfig.TransportType}'.", nameof(serverConfig));
-    }
 }

src/ModelContextProtocol/Configuration/McpServerConfig.cs

@@ -7,6 +7,7 @@
     <PackageId>ModelContextProtocol</PackageId>
     <Description>.NET SDK for the Model Context Protocol (MCP)</Description>
     <PackageReadmeFile>README.md</PackageReadmeFile>
+    <LangVersion>preview</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard2.0'">