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

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;
 }