Capture tool call name in ILogger logs on success and not just failure

src/ModelContextProtocol.Core/McpSessionHandler.cs

@@ -442,7 +442,8 @@
             // Now that the request has been sent, register for cancellation. If we registered before,
             // a cancellation request could arrive before the server knew about that request ID, in which
             // case the server could ignore it.
-            LogRequestSentAwaitingResponse(EndpointName, request.Method, request.Id);
+            string? target = GetRequestTarget(request);
+            LogRequestSentAwaitingResponse(EndpointName, request.Method, request.Id, toolName: target);
             JsonRpcMessage? response;
             using (var registration = RegisterCancellation(cancellationToken, request))
             {
@@ -451,7 +452,7 @@
 
             if (response is JsonRpcError error)
             {
-                LogSendingRequestFailed(EndpointName, request.Method, error.Error.Message, error.Error.Code);
+                LogSendingRequestFailed(EndpointName, request.Method, error.Error.Message, error.Error.Code, toolName: target);
                 throw new McpProtocolException($"Request failed (remote): {error.Error.Message}", (McpErrorCode)error.Error.Code);
             }
 
@@ -464,11 +465,11 @@
 
                 if (_logger.IsEnabled(LogLevel.Trace))
                 {
-                    LogRequestResponseReceivedSensitive(EndpointName, request.Method, success.Result?.ToJsonString() ?? "null");
+                    LogRequestResponseReceivedSensitive(EndpointName, request.Method, success.Result?.ToJsonString() ?? "null", toolName: target);
                 }
                 else
                 {
-                    LogRequestResponseReceived(EndpointName, request.Method);
+                    LogRequestResponseReceived(EndpointName, request.Method, toolName: target);
                 }
 
                 return success;
@@ -769,6 +770,29 @@
         return null;
     }
 
+    /// <summary>
+    /// Extracts the target identifier (tool name, prompt name, or resource URI) from a request.
+    /// </summary>
+    /// <param name="request">The JSON-RPC request.</param>
+    /// <returns>The target identifier if available; otherwise, null.</returns>
+    private static string? GetRequestTarget(JsonRpcRequest request)
+    {
+        if (request.Params is not JsonObject paramsObj)
+        {
+            return null;
+        }
+
+        return request.Method switch
+        {
+            RequestMethods.ToolsCall => GetStringProperty(paramsObj, "name"),
+            RequestMethods.PromptsGet => GetStringProperty(paramsObj, "name"),
+            RequestMethods.ResourcesRead => GetStringProperty(paramsObj, "uri"),
+            RequestMethods.ResourcesSubscribe => GetStringProperty(paramsObj, "uri"),
+            RequestMethods.ResourcesUnsubscribe => GetStringProperty(paramsObj, "uri"),
+            _ => null
+        };
+    }
+
     [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} message processing canceled.")]
     private partial void LogEndpointMessageProcessingCanceled(string endpointName);
 
@@ -784,8 +808,8 @@
     [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} received request for unknown request ID '{RequestId}'.")]
     private partial void LogNoRequestFoundForMessageWithId(string endpointName, RequestId requestId);
 
-    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} request failed for method '{Method}': {ErrorMessage} ({ErrorCode}).")]
-    private partial void LogSendingRequestFailed(string endpointName, string method, string errorMessage, int errorCode);
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} request failed for method '{Method}' (target: '{ToolName}'): {ErrorMessage} ({ErrorCode}).")]
+    private partial void LogSendingRequestFailed(string endpointName, string method, string errorMessage, int errorCode, string? targetName = null);
 
     [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} received invalid response for method '{Method}'.")]
     private partial void LogSendingRequestInvalidResponseType(string endpointName, string method);
@@ -799,11 +823,11 @@
     [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} canceled request '{RequestId}' per client notification. Reason: '{Reason}'.")]
     private partial void LogRequestCanceled(string endpointName, RequestId requestId, string? reason);
 
-    [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} Request response received for method {method}")]
-    private partial void LogRequestResponseReceived(string endpointName, string method);
+    [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} Request response received for method {method} (tool: '{ToolName}')")]
+    private partial void LogRequestResponseReceived(string endpointName, string method, string? toolName = null);
 
-    [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} Request response received for method {method}. Response: '{Response}'.")]
-    private partial void LogRequestResponseReceivedSensitive(string endpointName, string method, string response);
+    [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} Request response received for method {method} (tool: '{ToolName}'). Response: '{Response}'.")]
+    private partial void LogRequestResponseReceivedSensitive(string endpointName, string method, string response, string? toolName = null);
 
     [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} read {MessageType} message from channel.")]
     private partial void LogMessageRead(string endpointName, string messageType);
@@ -820,8 +844,8 @@
     [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} received request for method '{Method}', but no handler is available.")]
     private partial void LogNoHandlerFoundForRequest(string endpointName, string method);
 
-    [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} waiting for response to request '{RequestId}' for method '{Method}'.")]
-    private partial void LogRequestSentAwaitingResponse(string endpointName, string method, RequestId requestId);
+    [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} waiting for response to request '{RequestId}' for method '{Method}' (tool: '{ToolName}').")]
+    private partial void LogRequestSentAwaitingResponse(string endpointName, string method, RequestId requestId, string? toolName = null);
 
     [LoggerMessage(Level = LogLevel.Debug, Message = "{EndpointName} sending message.")]
     private partial void LogSendingMessage(string endpointName);

tests/Common/Utils/MockLoggerProvider.cs

@@ -6,6 +6,7 @@ namespace ModelContextProtocol.Tests.Utils;
 public class MockLoggerProvider() : ILoggerProvider
 {
     public ConcurrentQueue<(string Category, LogLevel LogLevel, EventId EventId, string Message, Exception? Exception)> LogMessages { get; } = [];
+    public ConcurrentQueue<(string Category, LogLevel LogLevel, EventId EventId, string Message, Exception? Exception, object? State)> LogMessagesWithState { get; } = [];
 
     public ILogger CreateLogger(string categoryName)
     {
@@ -22,6 +23,7 @@ public void Log<TState>(
             LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
         {
             mockProvider.LogMessages.Enqueue((category, logLevel, eventId, formatter(state, exception), exception));
+            mockProvider.LogMessagesWithState.Enqueue((category, logLevel, eventId, formatter(state, exception), exception, state));
         }
 
         public bool IsEnabled(LogLevel logLevel) => true;

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsToolsTests.cs

@@ -20,13 +20,20 @@ namespace ModelContextProtocol.Tests.Configuration;
 
 public partial class McpServerBuilderExtensionsToolsTests : ClientServerTestBase
 {
+    private MockLoggerProvider _mockLoggerProvider = new();
+
     public McpServerBuilderExtensionsToolsTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper)
     {
+        // Configure LoggerFactory to use Debug level and add MockLoggerProvider
+        LoggerFactory = Microsoft.Extensions.Logging.LoggerFactory.Create(builder =>
+        {
+            builder.AddProvider(XunitLoggerProvider);
+            builder.AddProvider(_mockLoggerProvider);
+            builder.SetMinimumLevel(LogLevel.Debug);
+        });
     }
 
-    private MockLoggerProvider _mockLoggerProvider = new();
-
     protected override void ConfigureServices(ServiceCollection services, IMcpServerBuilder mcpServerBuilder)
     {
         mcpServerBuilder
@@ -733,6 +740,86 @@ await client.SendNotificationAsync(
         await Assert.ThrowsAnyAsync<OperationCanceledException>(async () => await invokeTask);
     }
 
+    [Fact]
+    public async Task ToolName_Captured_In_Structured_Logging()
+    {
+        await using McpClient client = await CreateMcpClientForServer();
+
+        // Call a tool that will succeed
+        var result = await client.CallToolAsync(
+            "echo",
+            new Dictionary<string, object?> { ["message"] = "test" },
+            cancellationToken: TestContext.Current.CancellationToken);
+
+        Assert.NotNull(result);
+
+        // Verify that the tool name is captured in structured logging
+        // The LogMessagesWithState should contain log entries with tool name in the state
+        var relevantLogs = _mockLoggerProvider.LogMessagesWithState
+            .Where(m => m.Category == "ModelContextProtocol.Client.McpClient" && 
+                        m.Message.Contains("tools/call"))
+            .ToList();
+
+        Assert.NotEmpty(relevantLogs);
+
+        // Check that at least one log entry has the tool name in its structured state
+        // This demonstrates how users can extract the tool name from TState in a custom ILoggerProvider
+        // The State object is IReadOnlyList<KeyValuePair<string, object?>> which contains
+        // structured logging parameters like "ToolName", "Method", "EndpointName", etc.
+        bool foundToolName = relevantLogs.Any(log =>
+        {
+            if (log.State is IReadOnlyList<KeyValuePair<string, object?>> stateList)
+            {
+                return stateList.Any(kvp => 
+                    kvp.Key == "ToolName" && 
+                    kvp.Value?.ToString() == "echo");
+            }
+            return false;
+        });
+
+        Assert.True(foundToolName, "Tool name 'echo' was not found in structured logging state");
+    }
+
+    [Fact]
+    public async Task ToolName_Captured_In_Structured_Logging_OnToolError()
+    {
+        await using McpClient client = await CreateMcpClientForServer();
+
+        // Call a tool that will error - note that tool errors are returned as CallToolResult with IsError=true,
+        // not thrown as exceptions per the MCP spec
+        var result = await client.CallToolAsync(
+            "throw_exception",
+            cancellationToken: TestContext.Current.CancellationToken);
+
+        // Verify the tool error was returned properly
+        Assert.NotNull(result);
+        Assert.True(result.IsError);
+
+        // Verify that the tool name is captured in structured logging
+        // even when the tool encounters an error
+        var relevantLogs = _mockLoggerProvider.LogMessagesWithState
+            .Where(m => m.LogLevel == LogLevel.Debug &&
+                        (m.Message.Contains("waiting for response") || m.Message.Contains("response received")) &&
+                        m.Message.Contains("tools/call"))
+            .ToList();
+
+        Assert.NotEmpty(relevantLogs);
+
+        // Check that at least one log entry has the tool name in its structured state
+        bool foundToolName = relevantLogs.Any(log =>
+        {
+            if (log.State is IReadOnlyList<KeyValuePair<string, object?>> stateList)
+            {
+                return stateList.Any(kvp => 
+                    kvp.Key == "ToolName" && 
+                    kvp.Value?.ToString() == "throw_exception");
+            }
+            return false;
+        });
+
+        Assert.True(foundToolName, "Tool name 'throw_exception' was not found in structured logging state");
+    }
+
     [McpServerToolType]
     public sealed class EchoTool(ObjectWithId objectFromDI)
     {