MCP Observer SDK

A lightweight, decorator-based observability SDK for Model Context Protocol (MCP) tools. Add comprehensive telemetry and insights to your MCP servers with a single line of code.

Features

• Zero-friction Integration: Add observability with a simple decorator
• OpenTelemetry Support: Built-in tracing, metrics, and distributed context propagation
• Privacy-First: Configurable I/O tracking with dual-consent system
• Universal Compatibility: Works with all MCP tool function signatures
• Dual Storage: Durable storage for analytics + real-time streaming via OpenTelemetry
• Session Tracking: Automatic session and request correlation

Installation

From PyPI

pip install mcp-observer

Using uv (recommended)

uv pip install mcp-observer

For development

# Clone the repository
git clone https://github.com/yourusername/mcp-observer-sdk.git
cd mcp-observer-sdk

# Install in development mode
pip install -e ".[dev]"

Quick Start

from mcp_observer import MCPObserver
from fastmcp import FastMCP

# Initialize your MCP server
mcp = FastMCP("MyServer")

# Initialize the observer (project is automatically determined from your API key)
observer = MCPObserver(
    name="MyServer",
    version="1.0.0",
    api_key="your-generated-api-key"
)

# Decorate your tools
@mcp.tool()
@observer.track(track_io=True)
async def my_tool(data: dict) -> dict:
    # Your tool logic here
    return {"result": "success"}

Examples

Example 1: Simple Tool (No Context)

from mcp_observer import MCPObserver
from fastmcp import FastMCP

mcp = FastMCP("MathServer")
observer = MCPObserver(
    name="MathServer",
    version="1.0.0",
    api_key="your-api-key"
)

@mcp.tool(name="adder", description="Add two numbers")
@observer.track(track_io=True)
async def add(a: int, b: int) -> int:
    """Add two numbers together"""
    return a + b

Example 2: Tool with Session Context

from mcp_observer import MCPObserver
from fastmcp import FastMCP, Context
from typing import Optional

mcp = FastMCP("EchoServer")
observer = MCPObserver(
    name="EchoServer",
    version="1.0.0",
    api_key="your-api-key"
)

@mcp.tool(name="echo", description="Echo the input with session tracking")
@observer.track(track_io=True)
async def echo(message: str, ctx: Optional[Context] = None) -> str:
    """Echo input string with session ID"""
    if ctx:
        return f"{message} (Session: {ctx.session_id})"
    return message

Example 3: Fingerprint-Only Tracking (Default)

For tools that handle sensitive data, omit track_io=True to only store fingerprints:

@mcp.tool(name="process_sensitive_data")
@observer.track()  # Only fingerprints stored, no full I/O
async def process_sensitive_data(user_data: dict) -> dict:
    """Process sensitive user data"""
    # Only metadata is logged, not the actual data
    return {"status": "processed"}

Parameters on MCP Observer:

Constructor

• name: Name of your server or application (This is what appears in logging)
• version: Version of your server/application
• api_key: Your API key for authentication (project is automatically determined from this key)

Decorator: @observer.track()

• track_io (bool): If True, enables full input/output tracking (requires project consent)
  • Default: False (only fingerprints are stored)

Advanced Features

OpenTelemetry Integration

The SDK automatically integrates with OpenTelemetry for distributed tracing and metrics:

observer = MCPObserver(
    name="MyServer",
    version="1.0.0",
    api_key="your-api-key",
    otlp_endpoint="http://localhost:4317",  # Optional: Send to OTLP collector
    enable_console_export=True  # Optional: Enable console debugging
)

Environment Variables:

• OTEL_EXPORTER_OTLP_ENDPOINT: Configure OTLP endpoint for production tracing
• OTEL_CONSOLE_EXPORT: Set to "true" to enable console span/metric export

Automatic Metrics:

• mcp.tool.calls: Counter for tool invocations
• mcp.tool.duration: Histogram of tool execution times (ms)
• mcp.tool.errors: Counter for tool errors

Automatic Spans:

• Each tool call creates a span named mcp.tool.{function_name}
• Spans include: call_id, session_id, latency, status, error details

Tracking Policy System

The SDK uses a dual-consent system for full I/O tracking:

1. Developer declares safety: Use @observer.track(track_io=True)
2. Project admin enables: Backend API controls per-tool policy
3. Results are cached: Policy responses cached for 1 hour (configurable)

This ensures sensitive data is only stored when both developer and admin consent.

Custom Logging

Pass your own logger for integration with existing logging infrastructure:

import logging

my_logger = logging.getLogger("MyApp")
my_logger.setLevel(logging.DEBUG)

observer = MCPObserver(
    name="MyServer",
    version="1.0.0",
    api_key="your-api-key",
    logger=my_logger
)

Running the Example

# Install dependencies
uv pip install -e ".[dev]"

# Run the example server
python tests/simple_example.py

API Reference

MCPObserver(name, version, api_key, **kwargs)

Initialize the observer for your MCP server.

Parameters:

• name (str): Your server/application name
• version (str): Your server/application version
• api_key (str): Authentication key (project is auto-determined)
• otlp_endpoint (str, optional): OTLP collector endpoint
• enable_console_export (bool, optional): Enable console span/metric output
• logger (logging.Logger, optional): Custom logger instance

@observer.track(track_io=False)

Decorator to add observability to MCP tools.

Parameters:

• track_io (bool, optional): Enable full I/O tracking (requires project consent). Default: False

Returns:

• Decorated async function with telemetry

Development

Running Tests

# Install development dependencies
pip install -e ".[dev]"

# Run tests
pytest

# Run with coverage
pytest --cov=mcp_observer --cov-report=html

Code Quality

# Format code
black src tests

# Type checking
mypy src

# Linting
ruff check src tests

Project Structure

mcp-observer-sdk/
├── src/
│   └── mcp_observer/
│       ├── __init__.py          # Package exports
│       ├── observer.py          # Main MCPObserver class
│       └── wrapper.py           # Decorator and telemetry logic
├── tests/
│   └── simple_example.py        # Example MCP server
├── pyproject.toml               # Package configuration
├── README.md                    # This file
└── LICENSE                      # MIT License

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

• Issues: GitHub Issues
• Documentation: Full Documentation
• Email: support@yourdomain.com

Acknowledgments

• Built for the Model Context Protocol
• Powered by OpenTelemetry
• Inspired by the need for better MCP tool observability