Adding an overload of McpClientExtensions::CallToolAsync taking JsonElement tool argument

src/ModelContextProtocol.Core/Client/McpClientExtensions.cs

@@ -789,6 +789,101 @@ public static Task UnsubscribeFromResourceAsync(this IMcpClient client, Uri uri,
         return UnsubscribeFromResourceAsync(client, uri.ToString(), cancellationToken);
     }
 
+    /// <summary>
+    /// Invokes a tool on the server.
+    /// </summary>
+    /// <param name="client">The client instance used to communicate with the MCP server.</param>
+    /// <param name="toolName">The name of the tool to call on the server.</param>
+    /// <param name="arguments">A <see cref="JsonElement"/> containing arguments to pass to the tool. Each property represents a tool parameter name,
+    /// and its associated value represents the argument value as a <see cref="JsonElement"/>.
+    /// </param>
+    /// <param name="progress">
+    /// An optional <see cref="IProgress{T}"/> to have progress notifications reported to it. Setting this to a non-<see langword="null"/>
+    /// value will result in a progress token being included in the call, and any resulting progress notifications during the operation
+    /// routed to this instance.
+    /// </param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>
+    /// A task containing the <see cref="CallToolResult"/> from the tool execution. The response includes
+    /// the tool's output content, which may be structured data, text, or an error message.
+    /// </returns>
+    /// <exception cref="ArgumentNullException"><paramref name="client"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException"><paramref name="toolName"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentException"><paramref name="arguments"/> does not represent a JSON object.</exception>
+    /// <exception cref="McpException">The server could not find the requested tool, or the server encountered an error while processing the request.</exception>
+    /// <example>
+    /// <code>
+    /// // Call a tool with JsonElement arguments
+    /// var arguments = JsonDocument.Parse("""{"message": "Hello MCP!"}""").RootElement;
+    /// var result = await client.CallToolAsync("echo", arguments);
+    /// </code>
+    /// </example>
+    public static ValueTask<CallToolResult> CallToolAsync(
+        this IMcpClient client,
+        string toolName,
+        JsonElement arguments,
+        IProgress<ProgressNotificationValue>? progress = null,
+        CancellationToken cancellationToken = default)
+    {
+        Throw.IfNull(client);
+        Throw.IfNull(toolName);
+
+        if (arguments.ValueKind != JsonValueKind.Object)
+        {
+            throw new ArgumentException($"The arguments parameter must represent a JSON object, but was {arguments.ValueKind}.", nameof(arguments));
+        }
+
+        if (progress is not null)
+        {
+            return SendRequestWithProgressAsync(client, toolName, arguments, progress, cancellationToken);
+        }
+
+        return client.SendRequestAsync(
+            RequestMethods.ToolsCall,
+            new()
+            {
+                Name = toolName,
+                Arguments = arguments.EnumerateObject().ToDictionary(prop => prop.Name, prop => prop.Value) ?? []
+            },
+            McpJsonUtilities.JsonContext.Default.CallToolRequestParams,
+            McpJsonUtilities.JsonContext.Default.CallToolResult,
+            cancellationToken: cancellationToken);
+
+        static async ValueTask<CallToolResult> SendRequestWithProgressAsync(
+            IMcpClient client,
+            string toolName,
+            JsonElement arguments,
+            IProgress<ProgressNotificationValue> progress,
+            CancellationToken cancellationToken)
+        {
+            ProgressToken progressToken = new(Guid.NewGuid().ToString("N"));
+
+            await using var _ = client.RegisterNotificationHandler(NotificationMethods.ProgressNotification,
+                (notification, cancellationToken) =>
+                {
+                    if (JsonSerializer.Deserialize(notification.Params, McpJsonUtilities.JsonContext.Default.ProgressNotificationParams) is { } pn &&
+                        pn.ProgressToken == progressToken)
+                    {
+                        progress.Report(pn.Progress);
+                    }
+
+                    return default;
+                }).ConfigureAwait(false);
+
+            return await client.SendRequestAsync(
+                RequestMethods.ToolsCall,
+                new()
+                {
+                    Name = toolName,
+                    Arguments = arguments.EnumerateObject().ToDictionary(prop => prop.Name, prop => prop.Value) ?? [],
+                    ProgressToken = progressToken,
+                },
+                McpJsonUtilities.JsonContext.Default.CallToolRequestParams,
+                McpJsonUtilities.JsonContext.Default.CallToolResult,
+                cancellationToken: cancellationToken).ConfigureAwait(false);
+        }
+    }
+
     /// <summary>
     /// Invokes a tool on the server.
     /// </summary>

tests/ModelContextProtocol.Tests/ClientIntegrationTests.cs

@@ -96,6 +96,56 @@ public async Task CallTool_Stdio_EchoServer(string clientId)
         Assert.Equal("Echo: Hello MCP!", textContent.Text);
     }
 
+    [Theory]
+    [MemberData(nameof(GetClients))]
+    public async Task CallTool_Stdio_EchoServer_WithJsonElementArguments(string clientId)
+    {
+        // arrange
+        JsonElement arguments = JsonDocument.Parse("""
+        {
+          "message": "Hello MCP with JsonElement!"
+        }
+        """).RootElement;
+
+        // act
+        await using var client = await _fixture.CreateClientAsync(clientId);
+        var result = await client.CallToolAsync(
+            "echo",
+            arguments,
+            cancellationToken: TestContext.Current.CancellationToken
+        );
+
+        // assert
+        Assert.NotNull(result);
+        Assert.Null(result.IsError);
+        var textContent = Assert.Single(result.Content.OfType<TextContentBlock>());
+        Assert.Equal("Echo: Hello MCP with JsonElement!", textContent.Text);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetClients))]
+    public async Task CallTool_Stdio_EchoServer_WithJsonElementArguments_ThrowsForNonObject(string clientId)
+    {
+        // arrange - JsonElement representing a string, not an object
+        JsonElement stringArguments = JsonDocument.Parse("""
+        "Hello MCP!"
+        """).RootElement;
+
+        // act & assert
+        await using var client = await _fixture.CreateClientAsync(clientId);
+        var exception = await Assert.ThrowsAsync<ArgumentException>(async () =>
+            await client.CallToolAsync(
+                "echo",
+                stringArguments,
+                cancellationToken: TestContext.Current.CancellationToken
+            )
+        );
+
+        Assert.Contains("arguments parameter must represent a JSON object", exception.Message);
+        Assert.Contains("String", exception.Message);
+        Assert.Equal("arguments", exception.ParamName);
+    }
+
     [Fact]
     public async Task CallTool_Stdio_EchoSessionId_ReturnsEmpty()
     {