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| title | author | description | uid |
|---|---|---|---|
| Logging | mikekistler | How to use the logging feature in the MCP C# SDK. | logging |
Logging
MCP servers can expose log messages to clients through the Logging utility.
Important
Logging is deprecated as of MCP specification revision
2026-07-28(SEP-2577, MCP9005) and may be removed in a future version.
This document describes how to implement logging in MCP servers and how clients can consume log messages.
Logging levels
MCP uses the logging levels defined in RFC 5424.
The MCP C# SDK uses the standard .NET ILogger and ILoggerProvider abstractions, which support a slightly different set of logging levels. The following table shows the levels and how they map to standard .NET logging levels.
| Level | .NET | Description | Example use case |
|---|---|---|---|
debug |
✓ | Detailed debugging information | Function entry/exit points |
info |
✓ | General informational messages | Operation progress updates |
notice |
Normal but significant events | Configuration changes | |
warning |
✓ | Warning conditions | Deprecated feature usage |
error |
✓ | Error conditions | Operation failures |
critical |
✓ | Critical conditions | System component failures |
alert |
Action must be taken immediately | Data corruption detected | |
emergency |
System is unusable |
Note: .NET's ILogger also supports a Trace level (more verbose than Debug) log level.
As there is no more verbose level in the MCP logging levels, Trace level log messages are mapped to
the MCP debug level when sent to the client.
Server configuration and logging
MCP servers that implement the Logging utility must declare this in the capabilities sent in the Initialization phase at the beginning of the MCP session.
Servers built with the C# SDK always declare the logging capability. Doing so does not obligate the server to send log messages—only allows it. Note that stateless MCP servers might not be capable of sending log messages as there might not be an open connection to the client on which the log messages could be sent.
The C# SDK provides an extension method xref:Microsoft.Extensions.DependencyInjection.McpServerBuilderExtensions.WithSetLoggingLevelHandler* on xref:Microsoft.Extensions.DependencyInjection.IMcpServerBuilder to allow the server to perform any special logic it wants to perform when a client sets the logging level. However, the SDK already takes care of setting the xref:ModelContextProtocol.Server.McpServer.LoggingLevel in the xref:ModelContextProtocol.Server.McpServer, so most servers don't need to implement this.
MCP Servers using the MCP C# SDK can obtain an ILoggerProvider from the xref:ModelContextProtocol.Server.McpServer.AsClientLoggerProvider method on xref:ModelContextProtocol.Server.McpServer, and from that can create an ILogger instance for logging messages that should be sent to the MCP client.
Client support for logging
When the server indicates that it supports logging, clients should configure the logging level to specify which messages the server should send to the client.
Clients should check if the server supports logging by checking the xref:ModelContextProtocol.Protocol.ServerCapabilities.Logging property of the xref:ModelContextProtocol.Client.McpClient.ServerCapabilities field of xref:ModelContextProtocol.Client.McpClient.
If the server supports logging, the client should set the level of log messages it wishes to receive with the xref:ModelContextProtocol.Client.McpClient.SetLoggingLevelAsync* method on xref:ModelContextProtocol.Client.McpClient. If the client does not set a logging level, the server might choose to send all log messages or none—this is not specified in the protocol. So it's important that the client sets a logging level to ensure it receives the desired log messages and only those messages.
The loggingLevel set by the client is an MCP logging level.
For the mapping between MCP and .NET logging levels, see the Logging Levels section.
Lastly, the client must configure a notification handler for xref:ModelContextProtocol.Protocol.NotificationMethods.LoggingMessageNotification notifications. The following example simply writes the log messages to the console.