Overhaul tool handling (#89)

* Overhaul tool handling

- Renames [McpTool{Type}] to [McpServerTool{Type}], in order to distinguish representations of tools on the server from tools on the client.
- Enables [McpServerTool] methods to have arguments injected from DI, as well as a specific set of types from the implementation directly, like IMcpServer.
- Renames WithTools to WithToolsFromAssembly.
- All of the WithToolsXx methods now publish each individual McpServerTool into DI; other code can do so as well. The options setup code gathers all of the tools from DI and combines them into a collection which is then stored in McpServerOptions and used to construct the server.
- The server tools specified via DI as well as manually-provided handlers, using CallToolHandler as a fallback in case the requested tool doesn't exist in the tools collection, and ListToolsHandler augments the information for whatever tools exist.
- The tools are stored in McpServerOptions in a new McpServerToolCollection type, which is a thread-safe container that exposes add/removal notification. Adding/removing tools triggers a change notification that in turn sends a notification to the client about a tools update.
- The ServerOptions are exposed from the server instance.
- Removed cursor-based APIs from McpClientExtensions.
- Changed McpClientExtensions APIs to return `Task<IList<...>` rather than `IAsyncEnumerable<...>`.

I'm sure this will need to evolve further before we're "done", but it's a significant improvement from where we are now. One area I'm not super happy with is the notifying collection; that might work ok for a stdio server, where you can grab the created collection from the server's options and mutate it, but I don't know how well that's going to work for sse servers.

* Make McpServerTool{Collection} extensible

* Fix README.md example

* Add notifications test

* Address feedback

README.MD

@@ -44,7 +44,7 @@ await foreach (var tool in client.ListToolsAsync())
 // Execute a tool (this would normally be driven by LLM tool invocations).
 var result = await client.CallToolAsync(
     "echo",
-    new() { ["message"] = "Hello MCP!" },
+    new Dictionary<string, object?>() { ["message"] = "Hello MCP!" },
     CancellationToken.None);
 
 // echo always returns one and only one text content object
@@ -59,16 +59,13 @@ Tools can be exposed easily as `AIFunction` instances so that they are immediate
 
 ```csharp
 // Get available functions.
-IList<AIFunction> tools = await client.GetAIFunctionsAsync();
+IList<McpClientTool> tools = await client.ListToolsAsync();
 
 // Call the chat client using the tools.
 IChatClient chatClient = ...;
 var response = await chatClient.GetResponseAsync(
     "your prompt here",
-    new()
-    {
-        Tools = [.. tools],
-    });
+    new() { Tools = [.. tools] },
 ```
 
 ## Getting Started (Server)
@@ -88,17 +85,47 @@ var builder = Host.CreateEmptyApplicationBuilder(settings: null);
 builder.Services
     .AddMcpServer()
     .WithStdioServerTransport()
-    .WithTools();
+    .WithToolsFromAssembly();
 await builder.Build().RunAsync();
 
-[McpToolType]
+[McpServerToolType]
 public static class EchoTool
 {
-    [McpTool, Description("Echoes the message back to the client.")]
+    [McpServerTool, Description("Echoes the message back to the client.")]
     public static string Echo(string message) => $"hello {message}";
 }
 ```
 
+Tools can have the `IMcpServer` representing the server injected via a parameter to the method, and can use that for interaction with 
+the connected client. Similarly, arguments may be injected via dependency injection. For example, this tool will use the supplied 
+`IMcpServer` to make sampling requests back to the client in order to summarize content it downloads from the specified url via
+an `HttpClient` injected via dependency injection.
+```csharp
+[McpServerTool("SummarizeContentFromUrl"), Description("Summarizes content downloaded from a specific URI")]
+public static async Task<string> SummarizeDownloadedContent(
+    IMcpServer thisServer,
+    HttpClient httpClient,
+    [Description("The url from which to download the content to summarize")] string url,
+    CancellationToken cancellationToken)
+{
+    string content = await httpClient.GetStringAsync(url);
+
+    ChatMessage[] messages =
+    [
+        new(ChatRole.User, "Briefly summarize the following downloaded content:"),
+        new(ChatRole.User, content),
+    ]
+
+    ChatOptions options = new()
+    {
+        MaxOutputTokens = 256,
+        Temperature = 0.3f,
+    };
+
+    return $"Summary: {await thisServer.AsSamplingChatClient().GetResponseAsync(messages, options, cancellationToken)}";
+}
+```
+
 More control is also available, with fine-grained control over configuring the server and how it should handle client requests. For example:
 
 ```csharp
@@ -124,14 +151,18 @@ McpServerOptions options = new()
                         {
                             Name = "echo",
                             Description = "Echoes the input back to the client.",
-                            InputSchema = new JsonSchema()
-                            {
-                                Type = "object",
-                                Properties = new Dictionary<string, JsonSchemaProperty>()
+                            InputSchema = JsonSerializer.Deserialize<JsonElement>("""
                                 {
-                                    ["message"] = new JsonSchemaProperty() { Type = "string", Description = "The input to echo back." }
+                                    "type": "object",
+                                    "properties": {
+                                      "message": {
+                                        "type": "string",
+                                        "description": "The input to echo back"
+                                      }
+                                    },
+                                    "required": ["message"]
                                 }
-                            },
+                                """),
                         }
                     ]
                 };

samples/AspNetCoreSseServer/Program.cs

@@ -2,7 +2,7 @@ using ModelContextProtocol;
 using AspNetCoreSseServer;
 
 var builder = WebApplication.CreateBuilder(args);
-builder.Services.AddMcpServer().WithTools();
+builder.Services.AddMcpServer().WithToolsFromAssembly();
 var app = builder.Build();
 
 app.MapGet("/", () => "Hello World!");

samples/AspNetCoreSseServer/Tools/EchoTool.cs

@@ -3,10 +3,10 @@ using System.ComponentModel;
 
 namespace TestServerWithHosting.Tools;
 
-[McpToolType]
+[McpServerToolType]
 public static class EchoTool
 {
-    [McpTool, Description("Echoes the input back to the client.")]
+    [McpServerTool, Description("Echoes the input back to the client.")]
     public static string Echo(string message)
     {
         return "hello " + message;

samples/AspNetCoreSseServer/Tools/SampleLlmTool.cs

@@ -1,51 +1,36 @@
-using ModelContextProtocol.Protocol.Types;
+using Microsoft.Extensions.AI;
 using ModelContextProtocol.Server;
 using System.ComponentModel;
 
 namespace TestServerWithHosting.Tools;
 
 /// <summary>
-/// This tool uses depenency injection and async method
+/// This tool uses dependency injection and async method
 /// </summary>
-[McpToolType]
-public class SampleLlmTool
+[McpServerToolType]
+public static class SampleLlmTool
 {
-    private readonly IMcpServer _server;
-
-    public SampleLlmTool(IMcpServer server)
-    {
-        _server = server ?? throw new ArgumentNullException(nameof(server));
-    }
-
-    [McpTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
-    public async Task<string> SampleLLM(
+    [McpServerTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
+    public static async Task<string> SampleLLM(
+        IMcpServer thisServer,
         [Description("The prompt to send to the LLM")] string prompt,
         [Description("Maximum number of tokens to generate")] int maxTokens,
         CancellationToken cancellationToken)
     {
-        var samplingParams = CreateRequestSamplingParams(prompt ?? string.Empty, "sampleLLM", maxTokens);
-        var sampleResult = await _server.RequestSamplingAsync(samplingParams, cancellationToken);
+        ChatMessage[] messages =
+        [
+            new(ChatRole.System, "You are a helpful test server."),
+            new(ChatRole.User, prompt),
+        ];
 
-        return $"LLM sampling result: {sampleResult.Content.Text}";
-    }
-
-    private static CreateMessageRequestParams CreateRequestSamplingParams(string context, string uri, int maxTokens = 100)
-    {
-        return new CreateMessageRequestParams()
+        ChatOptions options = new()
         {
-            Messages = [new SamplingMessage()
-                {
-                    Role = Role.User,
-                    Content = new Content()
-                    {
-                        Type = "text",
-                        Text = $"Resource {uri} context: {context}"
-                    }
-                }],
-            SystemPrompt = "You are a helpful test server.",
-            MaxTokens = maxTokens,
+            MaxOutputTokens = maxTokens,
             Temperature = 0.7f,
-            IncludeContext = ContextInclusion.ThisServer
         };
+
+        var samplingResponse = await thisServer.AsSamplingChatClient().GetResponseAsync(messages, options, cancellationToken);
+
+        return $"LLM sampling result: {samplingResponse}";
     }
 }

samples/ChatWithTools/ChatWithTools.csproj

@@ -11,7 +11,6 @@
     <PackageReference Include="Microsoft.Extensions.AI" />
     <PackageReference Include="Microsoft.Extensions.AI.OpenAI" />
     <PackageReference Include="Anthropic.SDK" />
-    <PackageReference Include="System.Linq.AsyncEnumerable" />
   </ItemGroup>
 
   <ItemGroup>

samples/ChatWithTools/Program.cs

@@ -19,7 +19,7 @@ var mcpClient = await McpClientFactory.CreateAsync(
 
 // Get all available tools
 Console.WriteLine("Tools available:");
-var tools = await mcpClient.GetAIFunctionsAsync();
+var tools = await mcpClient.ListToolsAsync();
 foreach (var tool in tools)
 {
     Console.WriteLine($"  {tool}");

samples/TestServerWithHosting/Program.cs

@@ -19,7 +19,7 @@ try
     builder.Services.AddSerilog();
     builder.Services.AddMcpServer()
         .WithStdioServerTransport()
-        .WithTools();
+        .WithToolsFromAssembly();
 
     var app = builder.Build();
 

samples/TestServerWithHosting/Tools/EchoTool.cs

@@ -3,10 +3,10 @@ using System.ComponentModel;
 
 namespace TestServerWithHosting.Tools;
 
-[McpToolType]
+[McpServerToolType]
 public static class EchoTool
 {
-    [McpTool, Description("Echoes the input back to the client.")]
+    [McpServerTool, Description("Echoes the input back to the client.")]
     public static string Echo(string message)
     {
         return "hello " + message;

samples/TestServerWithHosting/Tools/SampleLlmTool.cs

@@ -7,7 +7,7 @@ namespace TestServerWithHosting.Tools;
 /// <summary>
 /// This tool uses depenency injection and async method
 /// </summary>
-[McpToolType]
+[McpServerToolType]
 public class SampleLlmTool
 {
     private readonly IMcpServer _server;
@@ -17,7 +17,7 @@ public class SampleLlmTool
         _server = server ?? throw new ArgumentNullException(nameof(server));
     }
 
-    [McpTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
+    [McpServerTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
     public async Task<string> SampleLLM(
         [Description("The prompt to send to the LLM")] string prompt,
         [Description("Maximum number of tokens to generate")] int maxTokens,

src/Common/Polyfills/System/Collections/Generic/CollectionExtensions.cs

@@ -15,4 +15,7 @@ internal static class CollectionExtensions
 
         return dictionary.TryGetValue(key, out TValue? value) ? value : defaultValue;
     }
+
+    public static Dictionary<TKey, TValue> ToDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> source) =>
+        source.ToDictionary(kv => kv.Key, kv => kv.Value);
 }

src/ModelContextProtocol/AIContentExtensions.cs

@@ -0,0 +1,104 @@
+using Microsoft.Extensions.AI;
+using ModelContextProtocol.Protocol.Types;
+using ModelContextProtocol.Utils;
+using System.Runtime.InteropServices;
+
+namespace ModelContextProtocol;
+
+/// <summary>Provides helpers for conversions related to <see cref="AIContent"/>.</summary>
+public static class AIContentExtensions
+{
+    /// <summary>Creates a <see cref="ChatMessage"/> from a <see cref="PromptMessage"/>.</summary>
+    /// <param name="promptMessage">The message to convert.</param>
+    /// <returns>The created <see cref="ChatMessage"/>.</returns>
+    public static ChatMessage ToChatMessage(this PromptMessage promptMessage)
+    {
+        Throw.IfNull(promptMessage);
+
+        return new()
+        {
+            RawRepresentation = promptMessage,
+            Role = promptMessage.Role == Role.User ? ChatRole.User : ChatRole.Assistant,
+            Contents = [ToAIContent(promptMessage.Content)]
+        };
+    }
+
+    /// <summary>Creates a new <see cref="AIContent"/> from the content of a <see cref="Content"/>.</summary>
+    /// <param name="content">The <see cref="Content"/> to convert.</param>
+    /// <returns>The created <see cref="AIContent"/>.</returns>
+    public static AIContent ToAIContent(this Content content)
+    {
+        Throw.IfNull(content);
+
+        AIContent ac;
+        if (content is { Type: "image", MimeType: not null, Data: not null })
+        {
+            ac = new DataContent(Convert.FromBase64String(content.Data), content.MimeType);
+        }
+        else if (content is { Type: "resource" } && content.Resource is { } resourceContents)
+        {
+            ac = resourceContents.Blob is not null && resourceContents.MimeType is not null ?
+                new DataContent(Convert.FromBase64String(resourceContents.Blob), resourceContents.MimeType) :
+                new TextContent(resourceContents.Text);
+
+            (ac.AdditionalProperties ??= [])["uri"] = resourceContents.Uri;
+        }
+        else
+        {
+            ac = new TextContent(content.Text);
+        }
+
+        ac.RawRepresentation = content;
+
+        return ac;
+    }
+
+    /// <summary>Creates a new <see cref="AIContent"/> from the content of a <see cref="ResourceContents"/>.</summary>
+    /// <param name="content">The <see cref="ResourceContents"/> to convert.</param>
+    /// <returns>The created <see cref="AIContent"/>.</returns>
+    public static AIContent ToAIContent(this ResourceContents content)
+    {
+        Throw.IfNull(content);
+
+        AIContent ac = content.Blob is not null && content.MimeType is not null ?
+            new DataContent(Convert.FromBase64String(content.Blob), content.MimeType) :
+            new TextContent(content.Text);
+
+        (ac.AdditionalProperties ??= [])["uri"] = content.Uri;
+        ac.RawRepresentation = content;
+
+        return ac;
+    }
+
+    /// <summary>Creates a list of <see cref="AIContent"/> from a sequence of <see cref="Content"/>.</summary>
+    /// <param name="contents">The <see cref="Content"/> instances to convert.</param>
+    /// <returns>The created <see cref="AIContent"/> instances.</returns>
+    public static IList<AIContent> ToAIContents(this IEnumerable<Content> contents)
+    {
+        Throw.IfNull(contents);
+
+        return contents.Select(ToAIContent).ToList();
+    }
+
+    /// <summary>Creates a list of <see cref="AIContent"/> from a sequence of <see cref="ResourceContents"/>.</summary>
+    /// <param name="contents">The <see cref="ResourceContents"/> instances to convert.</param>
+    /// <returns>The created <see cref="AIContent"/> instances.</returns>
+    public static IList<AIContent> ToAIContents(this IEnumerable<ResourceContents> contents)
+    {
+        Throw.IfNull(contents);
+
+        return contents.Select(ToAIContent).ToList();
+    }
+
+    /// <summary>Extracts the data from a <see cref="DataContent"/> as a Base64 string.</summary>
+    internal static string GetBase64Data(this DataContent dataContent)
+    {
+#if NET
+        return Convert.ToBase64String(dataContent.Data.Span);
+#else
+        return MemoryMarshal.TryGetArray(dataContent.Data, out ArraySegment<byte> segment) ?
+            Convert.ToBase64String(segment.Array!, segment.Offset, segment.Count) :
+            Convert.ToBase64String(dataContent.Data.ToArray());
+#endif
+    }
+}

src/ModelContextProtocol/Client/McpClientExtensions.cs

@@ -3,8 +3,8 @@ using ModelContextProtocol.Protocol.Types;
 using ModelContextProtocol.Utils;
 using ModelContextProtocol.Utils.Json;
 using Microsoft.Extensions.AI;
-using System.Runtime.CompilerServices;
 using System.Text.Json;
+using System.Runtime.CompilerServices;
 
 namespace ModelContextProtocol.Client;
 
@@ -23,6 +23,7 @@ public static class McpClientExtensions
     public static Task SendNotificationAsync(this IMcpClient client, string method, object? parameters = null, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNullOrWhiteSpace(method);
 
         return client.SendMessageAsync(
             new JsonRpcNotification { Method = method, Params = parameters },
@@ -45,42 +46,67 @@ public static class McpClientExtensions
     }
 
     /// <summary>
-    /// Retrieves a sequence of available tools from the server.
+    /// Retrieves a list of available tools from the server.
     /// </summary>
     /// <param name="client">The client.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>An asynchronous sequence of tool information.</returns>
-    public static async IAsyncEnumerable<Tool> ListToolsAsync(
-        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
-    {
-        string? cursor = null;
-        do
-        {
-            var tools = await ListToolsAsync(client, cursor, cancellationToken).ConfigureAwait(false);
-            foreach (var tool in tools.Tools)
-            {
-                yield return tool;
-            }
-
-            cursor = tools.NextCursor;
-        }
-        while (cursor is not null);
-    }
-
-    /// <summary>
-    /// Retrieves a sequence of available tools from the server.
-    /// </summary>
-    /// <param name="client">The client.</param>
-    /// <param name="cursor">A cursor to paginate the results.</param>
-    /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>A task containing the server's response with tool information.</returns>
-    public static Task<ListToolsResult> ListToolsAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
+    /// <returns>A list of all available tools.</returns>
+    public static async Task<IList<McpClientTool>> ListToolsAsync(
+        this IMcpClient client, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
 
-        return client.SendRequestAsync<ListToolsResult>(
-            CreateRequest("tools/list", CreateCursorDictionary(cursor)),
-            cancellationToken);
+        List<McpClientTool>? tools = null;
+        string? cursor = null;
+        do
+        {
+            var toolResults = await client.SendRequestAsync<ListToolsResult>(
+                CreateRequest("tools/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            tools ??= new List<McpClientTool>(toolResults.Tools.Count);
+            foreach (var tool in toolResults.Tools)
+            {
+                tools.Add(new McpClientTool(client, tool));
+            }
+
+            cursor = toolResults.NextCursor;
+        }
+        while (cursor is not null);
+
+        return tools;
+    }
+
+    /// <summary>
+    /// Creates an enumerable for asynchronously enumerating all available tools from the server.
+    /// </summary>
+    /// <param name="client">The client.</param>
+    /// <param name="cancellationToken">A token to cancel the operation.</param>
+    /// <returns>An asynchronous sequence of all available tools.</returns>
+    /// <remarks>
+    /// Every iteration through the returned <see cref="IAsyncEnumerable{McpClientTool}"/>
+    /// will result in requerying the server and yielding the sequence of available tools.
+    /// </remarks>
+    public static async IAsyncEnumerable<McpClientTool> EnumerateToolsAsync(
+        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        Throw.IfNull(client);
+
+        string? cursor = null;
+        do
+        {
+            var toolResults = await client.SendRequestAsync<ListToolsResult>(
+                CreateRequest("tools/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            foreach (var tool in toolResults.Tools)
+            {
+                yield return new McpClientTool(client, tool);
+            }
+
+            cursor = toolResults.NextCursor;
+        }
+        while (cursor is not null);
     }
 
     /// <summary>
@@ -88,40 +114,69 @@ public static class McpClientExtensions
     /// </summary>
     /// <param name="client">The client.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>An asynchronous sequence of prompt information.</returns>
-    public static async IAsyncEnumerable<Prompt> ListPromptsAsync(
-        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    /// <returns>A list of all available prompts.</returns>
+    public static async Task<IList<Prompt>> ListPromptsAsync(
+        this IMcpClient client, CancellationToken cancellationToken = default)
     {
+        Throw.IfNull(client);
+
+        List<Prompt>? prompts = null;
+
         string? cursor = null;
         do
         {
-            var prompts = await ListPromptsAsync(client, cursor, cancellationToken).ConfigureAwait(false);
-            foreach (var prompt in prompts.Prompts)
+            var promptResults = await client.SendRequestAsync<ListPromptsResult>(
+                CreateRequest("prompts/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            if (prompts is null)
+            {
+                prompts = promptResults.Prompts;
+            }
+            else
+            {
+                prompts.AddRange(promptResults.Prompts);
+            }
+
+            cursor = promptResults.NextCursor;
+        }
+        while (cursor is not null);
+
+        return prompts;
+    }
+
+    /// <summary>
+    /// Creates an enumerable for asynchronously enumerating all available prompts from the server.
+    /// </summary>
+    /// <param name="client">The client.</param>
+    /// <param name="cancellationToken">A token to cancel the operation.</param>
+    /// <returns>An asynchronous sequence of all available prompts.</returns>
+    /// <remarks>
+    /// Every iteration through the returned <see cref="IAsyncEnumerable{Prompt}"/>
+    /// will result in requerying the server and yielding the sequence of available prompts.
+    /// </remarks>
+    public static async IAsyncEnumerable<Prompt> EnumeratePromptsAsync(
+        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        Throw.IfNull(client);
+
+        string? cursor = null;
+        do
+        {
+            var promptResults = await client.SendRequestAsync<ListPromptsResult>(
+                CreateRequest("prompts/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            foreach (var prompt in promptResults.Prompts)
             {
                 yield return prompt;
             }
 
-            cursor = prompts.NextCursor;
+            cursor = promptResults.NextCursor;
         }
         while (cursor is not null);
     }
 
-    /// <summary>
-    /// Retrieves a list of available prompts from the server.
-    /// </summary>
-    /// <param name="client">The client.</param>
-    /// <param name="cursor">A  cursor to paginate the results.</param>
-    /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>A task containing the server's response with prompt information.</returns>
-    public static Task<ListPromptsResult> ListPromptsAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
-    {
-        Throw.IfNull(client);
-
-        return client.SendRequestAsync<ListPromptsResult>(
-            CreateRequest("prompts/list", CreateCursorDictionary(cursor)),
-            cancellationToken);
-    }
-
     /// <summary>
     /// Retrieves a specific prompt with optional arguments.
     /// </summary>
@@ -130,9 +185,11 @@ public static class McpClientExtensions
     /// <param name="arguments">Optional arguments for the prompt</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
     /// <returns>A task containing the prompt's content and messages.</returns>
-    public static Task<GetPromptResult> GetPromptAsync(this IMcpClient client, string name, Dictionary<string, object>? arguments = null, CancellationToken cancellationToken = default)
+    public static Task<GetPromptResult> GetPromptAsync(
+        this IMcpClient client, string name, Dictionary<string, object?>? arguments = null, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNullOrWhiteSpace(name);
 
         return client.SendRequestAsync<GetPromptResult>(
             CreateRequest("prompts/get", CreateParametersDictionary(name, arguments)),
@@ -140,24 +197,69 @@ public static class McpClientExtensions
     }
 
     /// <summary>
-    /// Retrieves a sequence of available resource templates from the server.
+    /// Retrieves a list of available resource templates from the server.
     /// </summary>
     /// <param name="client">The client.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>An asynchronous sequence of resource template information.</returns>
-    public static async IAsyncEnumerable<ResourceTemplate> ListResourceTemplatesAsync(
-        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    /// <returns>A list of all available resource templates.</returns>
+    public static async Task<IList<ResourceTemplate>> ListResourceTemplatesAsync(
+        this IMcpClient client, CancellationToken cancellationToken = default)
     {
+        Throw.IfNull(client);
+
+        List<ResourceTemplate>? templates = null;
+
         string? cursor = null;
         do
         {
-            var resources = await ListResourceTemplatesAsync(client, cursor, cancellationToken).ConfigureAwait(false);
-            foreach (var resource in resources.ResourceTemplates)
+            var templateResults = await client.SendRequestAsync<ListResourceTemplatesResult>(
+                CreateRequest("resources/templates/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            if (templates is null)
             {
-                yield return resource;
+                templates = templateResults.ResourceTemplates;
+            }
+            else
+            {
+                templates.AddRange(templateResults.ResourceTemplates);
             }
 
-            cursor = resources.NextCursor;
+            cursor = templateResults.NextCursor;
+        }
+        while (cursor is not null);
+
+        return templates;
+    }
+
+    /// <summary>
+    /// Creates an enumerable for asynchronously enumerating all available resource templates from the server.
+    /// </summary>
+    /// <param name="client">The client.</param>
+    /// <param name="cancellationToken">A token to cancel the operation.</param>
+    /// <returns>An asynchronous sequence of all available resource templates.</returns>
+    /// <remarks>
+    /// Every iteration through the returned <see cref="IAsyncEnumerable{ResourceTemplate}"/>
+    /// will result in requerying the server and yielding the sequence of available resource templates.
+    /// </remarks>
+    public static async IAsyncEnumerable<ResourceTemplate> EnumerateResourceTemplatesAsync(
+        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        Throw.IfNull(client);
+
+        string? cursor = null;
+        do
+        {
+            var templateResults = await client.SendRequestAsync<ListResourceTemplatesResult>(
+                CreateRequest("resources/templates/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            foreach (var template in templateResults.ResourceTemplates)
+            {
+                yield return template;
+            }
+
+            cursor = templateResults.NextCursor;
         }
         while (cursor is not null);
     }
@@ -166,64 +268,81 @@ public static class McpClientExtensions
     /// Retrieves a list of available resources from the server.
     /// </summary>
     /// <param name="client">The client.</param>
-    /// <param name="cursor">A  cursor to paginate the results.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
-    public static Task<ListResourceTemplatesResult> ListResourceTemplatesAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
+    /// <returns>A list of all available resources.</returns>
+    public static async Task<IList<Resource>> ListResourcesAsync(
+        this IMcpClient client, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
 
-        return client.SendRequestAsync<ListResourceTemplatesResult>(
-            CreateRequest("resources/templates/list", CreateCursorDictionary(cursor)),
-            cancellationToken);
-    }
+        List<Resource>? resources = null;
 
-    /// <summary>
-    /// Retrieves a sequence of available resources from the server.
-    /// </summary>
-    /// <param name="client">The client.</param>
-    /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>An asynchronous sequence of resource information.</returns>
-    public static async IAsyncEnumerable<Resource> ListResourcesAsync(
-        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
-    {
         string? cursor = null;
         do
         {
-            var resources = await ListResourcesAsync(client, cursor, cancellationToken).ConfigureAwait(false);
-            foreach (var resource in resources.Resources)
+            var resourceResults = await client.SendRequestAsync<ListResourcesResult>(
+                CreateRequest("resources/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            if (resources is null)
+            {
+                resources = resourceResults.Resources;
+            }
+            else
+            {
+                resources.AddRange(resourceResults.Resources);
+            }
+
+            cursor = resourceResults.NextCursor;
+        }
+        while (cursor is not null);
+
+        return resources;
+    }
+
+    /// <summary>
+    /// Creates an enumerable for asynchronously enumerating all available resources from the server.
+    /// </summary>
+    /// <param name="client">The client.</param>
+    /// <param name="cancellationToken">A token to cancel the operation.</param>
+    /// <returns>An asynchronous sequence of all available resources.</returns>
+    /// <remarks>
+    /// Every iteration through the returned <see cref="IAsyncEnumerable{Resource}"/>
+    /// will result in requerying the server and yielding the sequence of available resources.
+    /// </remarks>
+    public static async IAsyncEnumerable<Resource> EnumerateResourcesAsync(
+        this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        Throw.IfNull(client);
+
+        string? cursor = null;
+        do
+        {
+            var resourceResults = await client.SendRequestAsync<ListResourcesResult>(
+                CreateRequest("resources/list", CreateCursorDictionary(cursor)),
+                cancellationToken).ConfigureAwait(false);
+
+            foreach (var resource in resourceResults.Resources)
             {
                 yield return resource;
             }
 
-            cursor = resources.NextCursor;
+            cursor = resourceResults.NextCursor;
         }
         while (cursor is not null);
     }
 
-    /// <summary>
-    /// Retrieves a list of available resources from the server.
-    /// </summary>
-    /// <param name="client">The client.</param>
-    /// <param name="cursor">A  cursor to paginate the results.</param>
-    /// <param name="cancellationToken">A token to cancel the operation.</param>
-    public static Task<ListResourcesResult> ListResourcesAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
-    {
-        Throw.IfNull(client);
-
-        return client.SendRequestAsync<ListResourcesResult>(
-            CreateRequest("resources/list", CreateCursorDictionary(cursor)),
-            cancellationToken);
-    }
-
     /// <summary>
     /// Reads a resource from the server.
     /// </summary>
     /// <param name="client">The client.</param>
     /// <param name="uri">The uri of the resource.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
-    public static Task<ReadResourceResult> ReadResourceAsync(this IMcpClient client, string uri, CancellationToken cancellationToken = default)
+    public static Task<ReadResourceResult> ReadResourceAsync(
+        this IMcpClient client, string uri, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNullOrWhiteSpace(uri);
 
         return client.SendRequestAsync<ReadResourceResult>(
             CreateRequest("resources/read", new() { ["uri"] = uri }),
@@ -267,6 +386,7 @@ public static class McpClientExtensions
     public static Task SubscribeToResourceAsync(this IMcpClient client, string uri, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNullOrWhiteSpace(uri);
 
         return client.SendRequestAsync<EmptyResult>(
             CreateRequest("resources/subscribe", new() { ["uri"] = uri }),
@@ -282,6 +402,7 @@ public static class McpClientExtensions
     public static Task UnsubscribeFromResourceAsync(this IMcpClient client, string uri, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNullOrWhiteSpace(uri);
 
         return client.SendRequestAsync<EmptyResult>(
             CreateRequest("resources/unsubscribe", new() { ["uri"] = uri }),
@@ -296,48 +417,17 @@ public static class McpClientExtensions
     /// <param name="arguments">Optional arguments for the tool.</param>
     /// <param name="cancellationToken">A token to cancel the operation.</param>
     /// <returns>A task containing the tool's response.</returns>
-    public static Task<CallToolResponse> CallToolAsync(this IMcpClient client, string toolName, Dictionary<string, object> arguments, CancellationToken cancellationToken = default)
+    public static Task<CallToolResponse> CallToolAsync(
+        this IMcpClient client, string toolName, IReadOnlyDictionary<string, object?>? arguments = null, CancellationToken cancellationToken = default)
     {
         Throw.IfNull(client);
+        Throw.IfNull(toolName);
 
         return client.SendRequestAsync<CallToolResponse>(
             CreateRequest("tools/call", CreateParametersDictionary(toolName, arguments)),
             cancellationToken);
     }
 
-    /// <summary>Gets <see cref="AIFunction"/> instances for all of the tools available through the specified <see cref="IMcpClient"/>.</summary>
-    /// <param name="client">The client for which <see cref="AIFunction"/> instances should be created.</param>
-    /// <param name="cancellationToken">A token to cancel the operation.</param>
-    /// <returns>A task containing a list of the available functions.</returns>
-    public static async Task<IList<AIFunction>> GetAIFunctionsAsync(this IMcpClient client, CancellationToken cancellationToken = default)
-    {
-        Throw.IfNull(client);
-
-        List<AIFunction> functions = [];
-        await foreach (var tool in client.ListToolsAsync(cancellationToken).ConfigureAwait(false))
-        {
-            functions.Add(AsAIFunction(client, tool));
-        }
-
-        return functions;
-    }
-
-    /// <summary>Gets an <see cref="AIFunction"/> for invoking <see cref="Tool"/> via this <see cref="IMcpClient"/>.</summary>
-    /// <param name="client">The client with which to perform the invocation.</param>
-    /// <param name="tool">The tool to be invoked.</param>
-    /// <returns>An <see cref="AIFunction"/> for performing the call.</returns>
-    /// <remarks>
-    /// This operation does not validate that <paramref name="tool"/> is valid for the specified <paramref name="client"/>.
-    /// If the tool is not valid for the client, it will fail when invoked.
-    /// </remarks>
-    public static AIFunction AsAIFunction(this IMcpClient client, Tool tool)
-    {
-        Throw.IfNull(client);
-        Throw.IfNull(tool);
-
-        return new McpAIFunction(client, tool);
-    }
-
     /// <summary>
     /// Converts the contents of a <see cref="CreateMessageRequestParams"/> into a pair of
     /// <see cref="IEnumerable{ChatMessage}"/> and <see cref="ChatOptions"/> instances to use
@@ -428,12 +518,7 @@ public static class McpClientExtensions
                     {
                         Type = "image",
                         MimeType = dc.MediaType,
-                        Data = Convert.ToBase64String(dc.Data
-#if NET
-                            .Span),
-#else
-                            .ToArray()),
-#endif
+                        Data = dc.GetBase64Data(),
                     };
                 }
             }
@@ -499,7 +584,8 @@ public static class McpClientExtensions
     private static Dictionary<string, object?>? CreateCursorDictionary(string? cursor) =>
         cursor != null ? new() { ["cursor"] = cursor } : null;
 
-    private static Dictionary<string, object?> CreateParametersDictionary(string nameParameter, Dictionary<string, object>? arguments)
+    private static Dictionary<string, object?> CreateParametersDictionary(
+        string nameParameter, IReadOnlyDictionary<string, object?>? arguments)
     {
         Dictionary<string, object?> parameters = new()
         {
@@ -526,20 +612,20 @@ public static class McpClientExtensions
         /// <inheritdoc/>
         public override JsonElement JsonSchema => tool.InputSchema;
 
+        /// <inheritdoc/>
+        public override JsonSerializerOptions JsonSerializerOptions => McpJsonUtilities.DefaultOptions;
+
         /// <inheritdoc/>
         protected async override Task<object?> InvokeCoreAsync(
             IEnumerable<KeyValuePair<string, object?>> arguments, CancellationToken cancellationToken)
         {
-            Throw.IfNull(arguments);
-
-            Dictionary<string, object> argDict = [];
-            foreach (var arg in arguments)
-            {
-                if (arg.Value is not null)
-                {
-                    argDict[arg.Key] = arg.Value;
-                }
-            }
+            IReadOnlyDictionary<string, object?> argDict =
+                arguments as IReadOnlyDictionary<string, object?> ??
+#if NET
+                arguments.ToDictionary();
+#else
+                arguments.ToDictionary(kv => kv.Key, kv => kv.Value);   
+#endif
 
             CallToolResponse result = await client.CallToolAsync(tool.Name, argDict, cancellationToken).ConfigureAwait(false);
             return JsonSerializer.SerializeToElement(result, McpJsonUtilities.JsonContext.Default.CallToolResponse);

src/ModelContextProtocol/Client/McpClientTool.cs

@@ -0,0 +1,43 @@
+using ModelContextProtocol.Protocol.Types;
+using ModelContextProtocol.Utils.Json;
+using Microsoft.Extensions.AI;
+using System.Text.Json;
+
+namespace ModelContextProtocol.Client;
+
+/// <summary>Provides an AI function that calls a tool through <see cref="IMcpClient"/>.</summary>
+public sealed class McpClientTool : AIFunction
+{
+    private readonly IMcpClient _client;
+    private readonly Tool _tool;
+
+    internal McpClientTool(IMcpClient client, Tool tool)
+    {
+        _client = client;
+        _tool = tool;
+    }
+
+    /// <inheritdoc/>
+    public override string Name => _tool.Name;
+
+    /// <inheritdoc/>
+    public override string Description => _tool.Description ?? string.Empty;
+
+    /// <inheritdoc/>
+    public override JsonElement JsonSchema => _tool.InputSchema;
+
+    /// <inheritdoc/>
+    public override JsonSerializerOptions JsonSerializerOptions => McpJsonUtilities.DefaultOptions;
+
+    /// <inheritdoc/>
+    protected async override Task<object?> InvokeCoreAsync(
+        IEnumerable<KeyValuePair<string, object?>> arguments, CancellationToken cancellationToken)
+    {
+        IReadOnlyDictionary<string, object?> argDict =
+            arguments as IReadOnlyDictionary<string, object?> ??
+            arguments.ToDictionary();
+
+        CallToolResponse result = await _client.CallToolAsync(_tool.Name, argDict, cancellationToken).ConfigureAwait(false);
+        return JsonSerializer.SerializeToElement(result, McpJsonUtilities.JsonContext.Default.CallToolResponse);
+    }
+}

src/ModelContextProtocol/Configuration/McpServerBuilderExtensions.Tools.cs

@@ -1,12 +1,9 @@
 using ModelContextProtocol.Configuration;
-using ModelContextProtocol.Protocol.Types;
 using ModelContextProtocol.Server;
 using ModelContextProtocol.Utils;
-using ModelContextProtocol.Utils.Json;
-using Microsoft.Extensions.AI;
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
-using System.Text.Json;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace ModelContextProtocol;
 
@@ -23,23 +20,17 @@ public static partial class McpServerBuilderExtensions
     /// <typeparam name="TTool">The tool type.</typeparam>
     /// <param name="builder">The builder instance.</param>
     /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
-    public static IMcpServerBuilder WithTool<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] TTool>(this IMcpServerBuilder builder)
+    public static IMcpServerBuilder WithTools<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] TTool>(
+        this IMcpServerBuilder builder)
     {
         Throw.IfNull(builder);
-        List<AIFunction> functions = [];
 
-        PopulateFunctions(typeof(TTool), functions);
-        return WithTools(builder, functions);
-    }
-    /// <summary>
-    /// Adds all tools marked with <see cref="McpToolTypeAttribute"/> from the current assembly to the server.
-    /// </summary>
-    /// <param name="builder">The builder instance.</param>
-    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
-    [RequiresUnreferencedCode(RequiresUnreferencedCodeMessage)]
-    public static IMcpServerBuilder WithTools(this IMcpServerBuilder builder)
-    {
-        return WithToolsFromAssembly(builder, Assembly.GetCallingAssembly());
+        foreach (var toolMethod in GetToolMethods(typeof(TTool)))
+        {
+            builder.Services.AddSingleton(services => McpServerTool.Create(toolMethod, services: services));
+        }
+
+        return builder;
     }
 
     /// <summary>
@@ -55,147 +46,42 @@ public static partial class McpServerBuilderExtensions
         Throw.IfNull(builder);
         Throw.IfNull(toolTypes);
 
-        List<AIFunction> functions = [];
-
         foreach (var toolType in toolTypes)
         {
-            if (toolType is null)
+            if (toolType is not null)
             {
-                throw new ArgumentNullException(nameof(toolTypes), $"A tool type provided by the enumerator was null.");
+                foreach (var toolMethod in GetToolMethods(toolType))
+                {
+                    builder.Services.AddSingleton(services => McpServerTool.Create(toolMethod, services: services));
+                }
             }
-
-            PopulateFunctions(toolType, functions);
         }
-
-        return WithTools(builder, functions);
-    }
-
-    /// <summary>
-    /// Adds tools to the server.
-    /// </summary>
-    /// <param name="builder">The builder instance.</param>
-    /// <param name="functions"><see cref="AIFunction"/> instances to use as the tools.</param>
-    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentNullException"><paramref name="functions"/> is <see langword="null"/>.</exception>
-    public static IMcpServerBuilder WithTools(this IMcpServerBuilder builder, params IEnumerable<AIFunction> functions)
-    {
-        Throw.IfNull(builder);
-        Throw.IfNull(functions);
-
-        List<Tool> tools = [];
-        Dictionary<string, Func<RequestContext<CallToolRequestParams>, CancellationToken, Task<CallToolResponse>>> callbacks = [];
-
-        foreach (AIFunction function in functions)
-        {
-            if (function is null)
-            {
-                throw new ArgumentNullException(nameof(functions), $"A function provided by the enumerator was null.");
-            }
-
-            tools.Add(new()
-            {
-                Name = function.Name,
-                Description = function.Description,
-                InputSchema = function.JsonSchema,
-            });
-
-            callbacks.Add(function.Name, async (request, cancellationToken) =>
-            {
-                cancellationToken.ThrowIfCancellationRequested();
-
-                object? result;
-                try
-                {
-                    result = await function.InvokeAsync((request.Params?.Arguments ?? [])!, cancellationToken).ConfigureAwait(false);
-                }
-                catch (Exception e) when (e is not OperationCanceledException)
-                {
-                    return new CallToolResponse()
-                    {
-                        IsError = true,
-                        Content = [new() { Text = e.Message, Type = "text" }],
-                    };
-                }
-
-                switch (result)
-                {
-                    case JsonElement je when je.ValueKind == JsonValueKind.Null:
-                        return new() { Content = [] };
-
-                    case JsonElement je when je.ValueKind == JsonValueKind.Array:
-                        return new() { Content = je.EnumerateArray().Select(x => new Content() { Text = x.ToString(), Type = "text" }).ToList() };
-
-                    default:
-                        return new() { Content = [new() { Text = result?.ToString(), Type = "text" }] };
-                }
-            });
-        }
-
-        builder.WithListToolsHandler((_, _) => Task.FromResult(new ListToolsResult() { Tools = tools }));
-
-        builder.WithCallToolHandler(async (request, cancellationToken) =>
-        {
-            if (request.Params is null || !callbacks.TryGetValue(request.Params.Name, out var callback))
-            {
-                throw new McpServerException($"Unknown tool '{request.Params?.Name}'");
-            }
-
-            return await callback(request, cancellationToken).ConfigureAwait(false);
-        });
-
+        
         return builder;
     }
 
     /// <summary>
-    /// Adds types marked with the <see cref="McpToolTypeAttribute"/> attribute from the given assembly as tools to the server.
+    /// Adds types marked with the <see cref="McpServerToolTypeAttribute"/> attribute from the given assembly as tools to the server.
     /// </summary>
     /// <param name="builder">The builder instance.</param>
-    /// <param name="assembly">The assembly to load the types from. Null to get the current assembly</param>
+    /// <param name="toolAssembly">The assembly to load the types from. Null to get the current assembly</param>
     /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
     [RequiresUnreferencedCode(RequiresUnreferencedCodeMessage)]
-    public static IMcpServerBuilder WithToolsFromAssembly(this IMcpServerBuilder builder, Assembly? assembly = null)
+    public static IMcpServerBuilder WithToolsFromAssembly(this IMcpServerBuilder builder, Assembly? toolAssembly = null)
     {
-        assembly ??= Assembly.GetCallingAssembly();
+        Throw.IfNull(builder);
 
-        List<Type> toolTypes = [];
+        toolAssembly ??= Assembly.GetCallingAssembly();
 
-        foreach (var type in assembly.GetTypes())
-        {
-            if (type.GetCustomAttribute<McpToolTypeAttribute>() is null)
-            {
-                continue;
-            }
-
-            foreach (var method in type.GetMethods(BindingFlags.Public | BindingFlags.Static))
-            {
-                if (method.GetCustomAttribute<McpToolAttribute>() is not null)
-                {
-                    toolTypes.Add(type);
-                    break;
-                }
-            }
-        }
-
-        return toolTypes.Count > 0 ?
-            WithTools(builder, toolTypes) :
-            builder;
+        return builder.WithTools(
+            from t in toolAssembly.GetTypes()
+            where t.GetCustomAttribute<McpServerToolTypeAttribute>() is not null
+            select t);
     }
 
-    private static void PopulateFunctions(
-        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type toolType, 
-        List<AIFunction> functions)
-    {
-        foreach (var method in toolType.GetMethods(BindingFlags.Public | BindingFlags.Static))
-        {
-            if (method.GetCustomAttribute<McpToolAttribute>() is not { } attribute)
-            {
-                continue;
-            }
-
-            functions.Add(AIFunctionFactory.Create(method, target: null, new()
-            {
-                Name = attribute.Name ?? method.Name,
-            }));
-        }
-    }
+    private static IEnumerable<MethodInfo> GetToolMethods(
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type toolType) =>
+        from method in toolType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static)
+        where method.GetCustomAttribute<McpServerToolAttribute>() is not null
+        select method;
 }

src/ModelContextProtocol/Configuration/McpServerOptionsSetup.cs

@@ -1,5 +1,4 @@
 using System.Reflection;
-using ModelContextProtocol.Protocol.Types;
 using ModelContextProtocol.Server;
 using Microsoft.Extensions.Options;
 using ModelContextProtocol.Utils;
@@ -7,30 +6,66 @@ using ModelContextProtocol.Utils;
 namespace ModelContextProtocol.Configuration;
 
 /// <summary>
-/// Configures the McpServerOptions using provided server handlers.
+/// Configures the McpServerOptions using addition services from DI.
 /// </summary>
 /// <param name="serverHandlers">The server handlers configuration options.</param>
-internal sealed class McpServerOptionsSetup(IOptions<McpServerHandlers> serverHandlers) : IConfigureOptions<McpServerOptions>
+/// <param name="serverTools">Tools individually registered.</param>
+internal sealed class McpServerOptionsSetup(
+    IOptions<McpServerHandlers> serverHandlers,
+    IEnumerable<McpServerTool> serverTools) : IConfigureOptions<McpServerOptions>
 {
     /// <summary>
     /// Configures the given McpServerOptions instance by setting server information
-    /// and applying custom server handlers.
+    /// and applying custom server handlers and tools.
     /// </summary>
     /// <param name="options">The options instance to be configured.</param>
     public void Configure(McpServerOptions options)
     {
         Throw.IfNull(options);
 
-        var assemblyName = Assembly.GetEntryAssembly()?.GetName();
-
-        // Set server information based on the entry assembly
-        options.ServerInfo = new Implementation
+        // Configure the option's server information based on the current process,
+        // if it otherwise lacks server information.
+        var assemblyName = (Assembly.GetEntryAssembly() ?? Assembly.GetCallingAssembly()).GetName();
+        if (options.ServerInfo is not { } serverInfo ||
+            serverInfo.Name is null ||
+            serverInfo.Version is null)
         {
-            Name = assemblyName?.Name ?? "McpServer",
-            Version = assemblyName?.Version?.ToString() ?? "1.0.0",
-        };
+            options.ServerInfo = options.ServerInfo is null ?
+                new()
+                {
+                    Name = assemblyName.Name ?? "McpServer",
+                    Version = assemblyName.Version?.ToString() ?? "1.0.0",
+                } :
+                options.ServerInfo with
+                {
+                    Name = options.ServerInfo.Name ?? assemblyName.Name ?? "McpServer",
+                    Version = options.ServerInfo.Version ?? assemblyName.Version?.ToString() ?? "1.0.0",
+                };
+        }
 
-        // Apply custom server handlers
+        // Collect all of the provided tools into a tools collection. If the options already has
+        // a collection, add to it, otherwise create a new one. We want to maintain the identity
+        // of an existing collection in case someone has provided their own derived type, wants
+        // change notifications, etc.
+        McpServerToolCollection toolsCollection = options.Capabilities?.Tools?.ToolCollection ?? [];
+        foreach (var tool in serverTools)
+        {
+            toolsCollection.TryAdd(tool);
+        }
+
+        if (!toolsCollection.IsEmpty)
+        {
+            options.Capabilities = options.Capabilities is null ?
+                new() { Tools = new() { ToolCollection = toolsCollection } } :
+                options.Capabilities with
+                {
+                    Tools = options.Capabilities.Tools is null ?
+                        new() { ToolCollection = toolsCollection } :
+                        options.Capabilities.Tools with { ToolCollection = toolsCollection },
+                };
+        }
+
+        // Apply custom server handlers.
         serverHandlers.Value.OverwriteWithSetHandlers(options);
     }
 }

src/ModelContextProtocol/Protocol/Transport/StdioServerTransport.cs

@@ -25,6 +25,7 @@ public sealed class StdioServerTransport : TransportBase, IServerTransport
     private readonly TextReader _stdInReader;
     private readonly Stream _stdOutStream;
 
+    private SemaphoreSlim _sendLock = new(1, 1);
     private Task? _readTask;
     private CancellationTokenSource? _shutdownCts;
 
@@ -137,6 +138,8 @@ public sealed class StdioServerTransport : TransportBase, IServerTransport
     /// <inheritdoc/>
     public override async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
     {
+        using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
+
         if (!IsConnected)
         {
             _logger.TransportNotConnected(EndpointName);

src/ModelContextProtocol/Protocol/Types/CallToolRequestParams.cs

@@ -16,5 +16,5 @@ public class CallToolRequestParams
     /// Optional arguments to pass to the tool.
     /// </summary>
     [System.Text.Json.Serialization.JsonPropertyName("arguments")]
-    public Dictionary<string,object>? Arguments { get; init; }    
+    public Dictionary<string,object>? Arguments { get; init; }
 }

src/ModelContextProtocol/Protocol/Types/Capabilities.cs

@@ -155,7 +155,7 @@ public record ResourcesCapability
 public record ToolsCapability
 {
     /// <summary>
-    /// Whether this server supports notifications for changes to the tool list.
+    /// Gets or sets whether this server supports notifications for changes to the tool list.
     /// </summary>
     [JsonPropertyName("listChanged")]
     public bool? ListChanged { get; init; }
@@ -171,4 +171,16 @@ public record ToolsCapability
     /// </summary>
     [JsonIgnore]
     public Func<RequestContext<CallToolRequestParams>, CancellationToken, Task<CallToolResponse>>? CallToolHandler { get; init; }
+
+    /// <summary>Gets or sets a collection of tools served by the server.</summary>
+    /// <remarks>
+    /// Tools will specified via <see cref="ToolCollection"/> augment the <see cref="ListToolsHandler"/> and
+    /// <see cref="CallToolHandler"/>, if provided. ListTools requests will output information about every tool
+    /// in <see cref="ToolCollection"/> and then also any tools output by <see cref="ListToolsHandler"/>, if it's
+    /// non-<see langword="null"/>. CallTool requests will first check <see cref="ToolCollection"/> for the tool
+    /// being requested, and if the tool is not found in the <see cref="ToolCollection"/>, any specified <see cref="CallToolHandler"/>
+    /// will be invoked as a fallback.
+    /// </remarks>
+    [JsonIgnore]
+    public McpServerToolCollection? ToolCollection { get; init; }
 }

src/ModelContextProtocol/Protocol/Types/ResourceTemplate.cs

@@ -1,6 +1,4 @@
-using ModelContextProtocol.Protocol.Types;
-
-using System.Text.Json.Serialization;
+using System.Text.Json.Serialization;
 
 namespace ModelContextProtocol.Protocol.Types;
 

src/ModelContextProtocol/Protocol/Types/Tool.cs

@@ -10,6 +10,8 @@ namespace ModelContextProtocol.Protocol.Types;
 /// </summary>
 public class Tool
 {
+    private JsonElement _inputSchema = McpJsonUtilities.DefaultMcpToolSchema;
+
     /// <summary>
     /// The name of the tool.
     /// </summary>
@@ -42,6 +44,4 @@ public class Tool
             _inputSchema = value;
         }
     }
-
-    private JsonElement _inputSchema = McpJsonUtilities.DefaultMcpToolSchema;
 }