log-demo

Purpose

Demonstrate MCP logging protocol

Description

The log-demo tool demonstrates how MCP servers can send structured logs to clients at different severity levels. This is primarily an educational tool that shows the MCP logging protocol in action.

MCP supports five standard log levels:

• debug: Detailed information for debugging
• info: General informational messages
• warning: Warning messages for potential issues
• error: Error messages for failures
• critical: Critical issues requiring immediate attention

This tool helps you understand how MCP logging works and can be used to test that your MCP client properly displays logs at different severity levels.

Parameters

Parameter	Type	Required	Description
level	enum	No	Log level: debug, info, warning, error, critical (default: info)
message	string	No	Custom message to log (default: auto-generated)

Example Usage

Ask Claude:

"Show me an example of MCP logging at the warning level"
"Demonstrate debug logging with message 'Testing debug output'"
"Use the log-demo tool to show all log levels"
"Send a critical level log message"

Response

# MCP Logging Protocol Demo

## Requested Log Level: WARNING
**Message:** This is a warning level log message
**Timestamp:** 2025-01-05T10:30:00.000Z

## All Log Levels Example

The MCP protocol supports structured logging at multiple levels.
Here are examples of each log level:

[DEBUG] Debug log: Detailed variable state
  Data: {"variable":"example","value":42}

[INFO] Info log: Operation completed successfully
  Data: {"operation":"demo","duration":"123ms"}

[WARNING] Warning log: Resource usage is high
  Data: {"memory":"85%","cpu":"70%"}

[ERROR] Error log: Failed to process request
  Data: {"errorCode":"DEMO_ERROR","retryable":true}

[CRITICAL] Critical log: System component failure
  Data: {"component":"example","action":"restart_required"}

Log Levels Explained

DEBUG

Used for detailed diagnostic information useful during development. Typically disabled in production.

Example use cases:

• Variable state dumps
• Function entry/exit traces
• Detailed request/response data

INFO

General informational messages about normal operations.

Example use cases:

• Operation completion
• Configuration changes
• User actions

WARNING

Potentially problematic situations that don't prevent operation.

Example use cases:

• High resource usage
• Deprecated feature usage
• Retryable failures

ERROR

Error events that might still allow the application to continue.

Example use cases:

• Failed requests
• Invalid input
• External service failures

CRITICAL

Severe errors that may cause the application to abort.

Example use cases:

• System component failures
• Data corruption
• Security breaches

Authentication

Required: No

The log-demo tool is a demonstration tool and does not require authentication.

How MCP Logging Works

When an MCP server sends logs:

1. Server generates log message with level and data
2. Log is sent through the MCP transport
3. Client receives log notification
4. Client displays log in its UI (console, panel, etc.)
5. Client may filter logs by level or store for later viewing

Clients can set minimum log level thresholds to control what they see.

Log Structure

Each MCP log message includes:

{
  level: "debug" | "info" | "warning" | "error" | "critical",
  message: string,           // Human-readable message
  data?: Record<string, any>, // Optional structured data
  logger?: string,           // Optional logger name/category
  timestamp: string          // ISO 8601 timestamp
}

Common Use Cases

Testing Client Log Display

"Show me an error log to test my client's error display"

Understanding Log Levels

"What's the difference between warning and error? Show examples"

Learning MCP Protocol

"How does MCP logging work? Demonstrate with examples"

Debugging Client Integration

"Send logs at all levels to verify my client handles them correctly"

Client Filtering

MCP clients can filter logs by:

• Minimum level: Only show logs at or above a certain level
• Logger name: Filter by specific logger categories
• Search: Text search within log messages

Example filtering scenarios:

• Production: Show only warning and above
• Development: Show all levels including debug
• Troubleshooting: Focus on error and critical only

Related Tools

• trigger-notification - Demonstrate MCP notification protocol
• sampling-demo - Demonstrate MCP sampling protocol
• roots-demo - Demonstrate MCP roots protocol

Next Steps

• All Tools - Return to tools overview
• Development Guide - Learn to build MCP tools
• MCP Protocol Specification - Full MCP protocol documentation