Add task calls for MCP client tools

docs/concepts/tasks/tasks.md

@@ -153,6 +153,24 @@ var result = await client.CallToolWithPollingAsync(
     cancellationToken: cancellationToken);
 ```
 
+When you already have an <xref:ModelContextProtocol.Client.McpClientTool> from
+<xref:ModelContextProtocol.Client.McpClient.ListToolsAsync*>, invoke it directly without rebuilding
+the protocol request. The tool overload uses the original server-facing name even after
+<xref:ModelContextProtocol.Client.McpClientTool.WithName*> and preserves metadata configured with
+<xref:ModelContextProtocol.Client.McpClientTool.WithMeta*>:
+
+```csharp
+var tools = await client.ListToolsAsync(cancellationToken: cancellationToken);
+var tool = tools.Single(tool => tool.Name == "long-running-tool");
+
+var result = await tool.CallWithPollingAsync(
+    new Dictionary<string, object?> { ["input"] = "value" },
+    cancellationToken: cancellationToken);
+```
+
+Use <xref:ModelContextProtocol.Extensions.Tasks.McpTasksClientToolExtensions.CallAsTaskAsync*> when
+you want the created task handle instead of automatic polling.
+
 #### Manual control
 
 Use <xref:ModelContextProtocol.Extensions.Tasks.McpTasksClientExtensions.CallToolAsTaskAsync*> to receive the raw

src/ModelContextProtocol.Core/Client/McpClientTool.cs

@@ -100,6 +100,15 @@ internal McpClientTool(
     /// </remarks>
     public Tool ProtocolTool { get; }
 
+    /// <summary>
+    /// Gets the <see cref="McpClient"/> used to invoke this tool.
+    /// </summary>
+    /// <remarks>
+    /// This property is useful when implementing extensions that need to perform operations associated
+    /// with the same client session as this tool.
+    /// </remarks>
+    public McpClient Client => _client;
+
     /// <inheritdoc/>
     public override string Name => _name;
 
@@ -211,36 +220,87 @@ public ValueTask<CallToolResult> CallAsync(
         IProgress<ProgressNotificationValue>? progress = null,
         RequestOptions? options = null,
         CancellationToken cancellationToken = default)
+    {
+        options = MergeOptions(options);
+
+        return _client.CallToolAsync(
+            ProtocolTool.Name,
+            arguments,
+            progress,
+            options,
+            cancellationToken);
+    }
+
+    /// <summary>
+    /// Creates protocol request parameters for invoking this tool.
+    /// </summary>
+    /// <param name="arguments">An optional dictionary of arguments to pass to the tool.</param>
+    /// <param name="options">Optional request options including metadata and serialization settings.</param>
+    /// <returns>
+    /// Request parameters that use the tool's original protocol name and include metadata configured by
+    /// <see cref="WithMeta"/> merged with metadata from <paramref name="options"/>.
+    /// </returns>
+    /// <remarks>
+    /// This method is intended for extensions that need to invoke a tool through a protocol operation other
+    /// than <see cref="CallAsync"/>. Metadata from <paramref name="options"/> takes precedence over metadata
+    /// configured by <see cref="WithMeta"/> when the same key appears in both.
+    /// </remarks>
+    public CallToolRequestParams CreateCallToolRequestParams(
+        IReadOnlyDictionary<string, object?>? arguments = null,
+        RequestOptions? options = null)
+    {
+        options = MergeOptions(options);
+
+        JsonSerializerOptions serializerOptions = options?.JsonSerializerOptions ?? JsonSerializerOptions;
+        serializerOptions.MakeReadOnly();
+        var typeInfo = serializerOptions.GetTypeInfo<object?>();
+
+        Dictionary<string, JsonElement>? serializedArguments = null;
+        if (arguments is not null)
+        {
+            serializedArguments = new(arguments.Count);
+            foreach (var argument in arguments)
+            {
+                serializedArguments.Add(
+                    argument.Key,
+                    argument.Value is JsonElement element ? element : JsonSerializer.SerializeToElement(argument.Value, typeInfo));
+            }
+        }
+
+        return new CallToolRequestParams
+        {
+            Name = ProtocolTool.Name,
+            Arguments = serializedArguments,
+            Meta = options?.GetMetaForRequest(),
+        };
+    }
+
+    private RequestOptions? MergeOptions(RequestOptions? options)
     {
         // If there's any metadata provided with WithMeta, we can't just pass along the options as-is,
         // and instead need to create new options that merges in _meta.
-        if (_meta is { } meta)
+        if (_meta is not { } meta)
         {
-            // Create a new RequestOptions, as we're going to need to store a new JsonObject for Meta (either
-            // _meta or _meta+options.Meta), and we don't want to mutate the user's options object.
-            RequestOptions newOptions = options?.Clone() ?? new();
+            return options;
+        }
+
+        // Create a new RequestOptions, as we're going to need to store a new JsonObject for Meta (either
+        // _meta or _meta+options.Meta), and we don't want to mutate the user's options object.
+        RequestOptions newOptions = options?.Clone() ?? new();
 
-            // If we also have newOptions.Meta, merge that with _meta into a new JsonObject, preferring
-            // the objects from newOptions.Meta in case of conflicts.
-            if (newOptions.Meta is { } newOptionsMeta)
+        // If we also have newOptions.Meta, merge that with _meta into a new JsonObject, preferring
+        // the objects from newOptions.Meta in case of conflicts.
+        if (newOptions.Meta is { } newOptionsMeta)
+        {
+            meta = (JsonObject)meta.DeepClone();
+            foreach (var p in newOptionsMeta)
             {
-                meta = (JsonObject)meta.DeepClone();
-                foreach (var p in newOptionsMeta)
-                {
-                    meta[p.Key] = p.Value?.DeepClone();
-                }
+                meta[p.Key] = p.Value?.DeepClone();
             }
-
-            newOptions.Meta = meta;
-            options = newOptions;
         }
 
-        return _client.CallToolAsync(
-            ProtocolTool.Name,
-            arguments,
-            progress,
-            options,
-            cancellationToken);
+        newOptions.Meta = meta;
+        return newOptions;
     }
 
     /// <summary>

src/ModelContextProtocol.Extensions.Tasks/Client/McpTasksClientToolExtensions.cs

@@ -0,0 +1,65 @@
+using ModelContextProtocol.Client;
+using ModelContextProtocol.Protocol;
+
+namespace ModelContextProtocol.Extensions.Tasks;
+
+/// <summary>
+/// Extension methods for task-aware operations on <see cref="McpClientTool"/> instances.
+/// </summary>
+public static class McpTasksClientToolExtensions
+{
+    /// <summary>
+    /// Calls a tool and returns either an immediate result or a created task.
+    /// </summary>
+    /// <param name="tool">The tool to invoke.</param>
+    /// <param name="arguments">An optional dictionary of arguments to pass to the tool.</param>
+    /// <param name="options">Optional request options including metadata and serialization settings.</param>
+    /// <param name="cancellationToken">The cancellation token to monitor.</param>
+    /// <returns>The immediate tool result or information about the created task.</returns>
+    public static ValueTask<ResultOrCreatedTask<CallToolResult>> CallAsTaskAsync(
+        this McpClientTool tool,
+        IReadOnlyDictionary<string, object?>? arguments = null,
+        RequestOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+#if NET
+        ArgumentNullException.ThrowIfNull(tool);
+#else
+        if (tool is null) throw new ArgumentNullException(nameof(tool));
+#endif
+
+        return tool.Client.CallToolAsTaskAsync(
+            tool.CreateCallToolRequestParams(arguments, options),
+            cancellationToken);
+    }
+
+    /// <summary>
+    /// Calls a tool and, if the server creates a task, polls it to completion.
+    /// </summary>
+    /// <param name="tool">The tool to invoke.</param>
+    /// <param name="arguments">An optional dictionary of arguments to pass to the tool.</param>
+    /// <param name="options">Optional request options including metadata and serialization settings.</param>
+    /// <param name="maxConsecutiveStuckPolls">
+    /// The maximum number of consecutive polls that may report input required without publishing a new input request.
+    /// </param>
+    /// <param name="cancellationToken">The cancellation token to monitor.</param>
+    /// <returns>The completed tool result.</returns>
+    public static ValueTask<CallToolResult> CallWithPollingAsync(
+        this McpClientTool tool,
+        IReadOnlyDictionary<string, object?>? arguments = null,
+        RequestOptions? options = null,
+        int maxConsecutiveStuckPolls = 60,
+        CancellationToken cancellationToken = default)
+    {
+#if NET
+        ArgumentNullException.ThrowIfNull(tool);
+#else
+        if (tool is null) throw new ArgumentNullException(nameof(tool));
+#endif
+
+        return tool.Client.CallToolWithPollingAsync(
+            tool.CreateCallToolRequestParams(arguments, options),
+            maxConsecutiveStuckPolls,
+            cancellationToken);
+    }
+}

tests/ModelContextProtocol.Tests/Client/McpClientTaskMethodsTests.cs

@@ -31,17 +31,26 @@ protected override void ConfigureServices(ServiceCollection services, IMcpServer
             {
                 DefaultPollIntervalMs = 50,
             })
-            .WithTools([McpServerTool.Create(
-            async (string input, CancellationToken ct) =>
-            {
-                await Task.Delay(50, ct);
-                return $"Processed: {input}";
-            },
-            new McpServerToolCreateOptions
-            {
-                Name = "test-tool",
-                Description = "A test tool"
-            })]);
+            .WithTools([
+                McpServerTool.Create(
+                    async (string input, CancellationToken ct) =>
+                    {
+                        await Task.Delay(50, ct);
+                        return $"Processed: {input}";
+                    },
+                    new McpServerToolCreateOptions
+                    {
+                        Name = "test-tool",
+                        Description = "A test tool"
+                    }),
+                McpServerTool.Create(
+                    (RequestContext<CallToolRequestParams> context) =>
+                        context.Params.Meta?["sharedKey"]?.GetValue<string>() ?? "missing",
+                    new McpServerToolCreateOptions
+                    {
+                        Name = "metadata-tool",
+                        Description = "Returns request metadata"
+                    })]);
     }
 
     private static IDictionary<string, JsonElement> CreateArguments(string key, string value)
@@ -133,6 +142,43 @@ public async Task CallToolAsync_PollsUntilCompletion_ReturnsResult()
         Assert.Equal("Processed: hello", textContent.Text);
     }
 
+    [Fact]
+    public async Task McpClientTool_CallAsTaskAsync_UsesProtocolName()
+    {
+        await using var client = await CreateMcpClientForServer();
+        var ct = TestContext.Current.CancellationToken;
+        var tools = await client.ListToolsAsync(cancellationToken: ct);
+        var tool = tools.Single(t => t.Name == "test-tool").WithName("model-facing-name");
+
+        var augmented = await tool.CallAsTaskAsync(
+            new Dictionary<string, object?> { ["input"] = "hello" },
+            cancellationToken: ct);
+
+        Assert.True(augmented.IsTask);
+        Assert.NotNull(augmented.TaskCreated);
+    }
+
+    [Fact]
+    public async Task McpClientTool_CallWithPollingAsync_PreservesAndMergesMetadata()
+    {
+        await using var client = await CreateMcpClientForServer();
+        var ct = TestContext.Current.CancellationToken;
+        var tools = await client.ListToolsAsync(cancellationToken: ct);
+        var tool = tools.Single(t => t.Name == "metadata-tool")
+            .WithName("model-facing-name")
+            .WithMeta(new() { ["sharedKey"] = "from-tool" });
+
+        var result = await tool.CallWithPollingAsync(
+            options: new RequestOptions
+            {
+                Meta = new() { ["sharedKey"] = "from-options" },
+            },
+            cancellationToken: ct);
+
+        var textContent = Assert.IsType<TextContentBlock>(Assert.Single(result.Content));
+        Assert.Equal("from-options", textContent.Text);
+    }
+
     [Fact]
     public async Task CancelTaskAsync_ForWorkingTask_Succeeds()
     {