Sse Server

A minimal MCP (Model Context Protocol) server implementation using Server-Sent Events (SSE) transport, demonstrating email sending capability. Unlike many MCP servers examples that use stdio transport, this is a remote SSE server that can be deployed via Docker to any hosting platform. This serves as a clean, easy-to-understand reference for building deployable MCP servers.

Note: This implementation prioritizes clarity and ease of understanding over production-ready features. It does not include comprehensive production aspects such as robust error handling, monitoring, security hardening, rate limiting, or scalability considerations that would be required for enterprise deployments.

Features

• SSE Transport: Server-Sent Events for remote MCP server deployment
• Docker Ready: Containerized for easy deployment to any cloud platform
• Simple Email Sending: Send emails via Postmark SMTP
• MCP Integration: Exposes email functionality as MCP tools
• Clean Architecture: Minimal dependencies and clear separation of concerns
• Configurable Logging: Console logging with optional log level override
• Environment-based Configuration: Uses .env files for setup

Quick Start

1. Environment Setup

Copy .env.example to .env and update with your configuration:

cp .env.example .env

Then edit .env with your values:

# Required
MCP_SERVER_AUTH_KEY=your-mcp-auth-key
POSTMARK_API_KEY=your-postmark-api-key
[email protected]

# Optional
LOG_LEVEL=INFO
ENVIRONMENT=development

# Docker/Deployment Specific (optional)
FILE_LOGGING=true

2. Installation

First, install uv (see Astral's installation guide):

# Create virtual environment and install dependencies
uv venv

# Activate the virtual environment
# On macOS/Linux:
source .venv/bin/activate
# On Windows:
# .venv\Scripts\activate

uv sync  # Install dependencies into virtual environment

3. Run the Server

uv run python mcp_server.py

Deployment

Docker Deployment

# Build and run
docker build -f deployment/Dockerfile -t mcp-sse-server .
docker run -d --name mcp-sse-server -p 8080:8080 --env-file .env mcp-sse-server

Azure Container Apps Deployment

Quick Deploy

cd deployment/bicep
chmod +x deploy.sh
./deploy.sh

Custom Deployment Options

The deployment script now reads BASE_NAME and REGION_CODE from your .env file by default. For one-off deployments, you can override these:

# Use custom names from environment variables
export BASE_NAME=myclient-mcp REGION_CODE=eastus
./deploy.sh

# Or override via command line (takes precedence over .env)
./deploy.sh --base-name myclient-mcp --environment prod --region-code eastus

# Update code only (no infrastructure changes)
./deploy.sh --update

Azure Resources Created

The deployment creates these Azure resources following standard naming conventions:

Resource	Name Pattern	Example
Resource Group	rg-{service}-{env}-{region}	rg-mcp-sse-dev-weu
Container App	ca-{service}-{env}-{region}	ca-mcp-sse-dev-weu
Container App Environment	cae-{service}-{env}-{region}	cae-mcp-sse-dev-weu
Log Analytics Workspace	log-{service}-{env}-{region}	log-mcp-sse-dev-weu
Container Registry	cr{service}{env}{region}	crmcpssedevweu

Configuration:

• CPU: 0.5 vCPU, Memory: 1GB
• Fixed scaling: 1 replica (min=1, max=1)
• HTTPS ingress enabled

Prerequisites

• Azure CLI installed and configured
• Docker installed and running
• .env file with required variables

Live Deployment

The service is currently deployed at:

• URL: https://ca-mcp-sse-development-weu.mangosea-a4cea9ef.westeurope.azurecontainerapps.io
• Environment: Development (West Europe)
• Resource Group: rg-mcp-sse-dev-weu

Azure Management

Portal Access:

1. Navigate to Azure Portal
2. Search for resource group: rg-mcp-sse-dev-weu
3. Find container app: ca-mcp-sse-development-weu

CLI Commands:

# Get container app details
az containerapp show --name ca-mcp-sse-development-weu --resource-group rg-mcp-sse-dev-weu

# View logs
az containerapp logs show --name ca-mcp-sse-development-weu --resource-group rg-mcp-sse-dev-weu

# Restart app
az containerapp restart --name ca-mcp-sse-development-weu --resource-group rg-mcp-sse-dev-weu

Troubleshooting

Common Issues:

1. Missing Environment Variables: Ensure .env file exists with all required variables
2. Azure CLI Issues: Verify login with az account show
3. Container Failures: Check Docker daemon is running
4. Runtime Issues: Review container logs in Azure Log Analytics

Health Check:

curl https://your-container-app-url.azurecontainerapps.io/health

Local Development with ngrok

For local development with web clients, you can use ngrok to expose your local server:

1. Install ngrok: https://ngrok.com/download
2. Start your local MCP server:

   uv run python mcp_server.py
   

3. In another terminal, expose the server:

   ngrok http 8080
   

4. Use the provided HTTPS URL (e.g., https://abc123.ngrok.io) in your web client
5. Remember to include your X-API-Key header when making requests

Testing with AI Buddy

You can test your MCP SSE server in AI Buddy using ngrok to create a secure tunnel:

1. Start your local server:

   uv run python mcp_server.py
   

2. Create an ngrok tunnel:

   ngrok http 8080
   

3. Configure AI Buddy MCP connector:

   • Open AI Buddy and create a new MCP connector
   • Set the server URL to your ngrok public URL with /sse endpoint
   • Example: https://abc123.ngrok.io/sse
   • Set the X-API-Key header value to match your MCP_SERVER_AUTH_KEY from .env

4. Test the connection:

   • AI Buddy should now be able to connect to your local MCP server
   • Ask the expert to reveal what tool calls it has access to
   • You should see a request come through ngrok and the app server (in console )output
   • The expert should include in its list of tools the email sending tool
   • You can then request it to send a test email

Project Structure

mcp-sse-server/
├── mcp_server.py           # Main entry point and core application logic
├── src/                    # Main source code
│   ├── __init__.py         # Package marker
│   ├── config.py           # Configuration management
│   ├── mcp_tools.py        # MCP server and tools registration
│   ├── utils/              # Utility modules
│   │   ├── __init__.py     # Package marker
│   │   └── email.py        # Email utilities (moved from email_utils.py)
│   └── actions/            # MCP action implementations
│       ├── __init__.py     # Package marker
│       └── send_email.py   # Email sending action
├── tests/                  # Test files
│   ├── test_config.py      # Configuration tests
│   ├── test_email_utils.py # Email utility tests
│   ├── test_mcp_tools.py   # MCP tools tests
│   └── test_*.py           # Other test files
├── deployment/             # Deployment files
│   ├── Dockerfile          # Container configuration
│   └── bicep/              # Azure Bicep templates and scripts
│       ├── deploy.sh       # Automated deployment script
│       └── main.bicep      # Azure resource definitions
├── logs/                   # Runtime logs (created automatically)
├── pyproject.toml          # Dependencies and project config
└── README.md              # This file

Configuration

Environment Variables

Required:

• MCP_SERVER_AUTH_KEY: Authentication key for MCP requests
• POSTMARK_API_KEY: Your Postmark API key for sending emails
• SENDER_EMAIL: The email address to send from

Optional:

• LOG_LEVEL: Logging level (default: INFO)
• ENVIRONMENT: Environment name (default: development)
• FILE_LOGGING: Enable file logging (used in Docker containers)

Development

Actions System - Adding New MCP Tools

The server uses a transparent actions-based architecture where each MCP tool is implemented as a separate action module. Dependencies are explicitly declared in function signatures, making the system easy to understand and extend.

Directory Structure

src/actions/
├── __init__.py          # Package marker
├── send_email.py        # Email sending functionality
└── status.py            # Server status functionality (no dependencies)

How It Works

The system uses a dependency registry approach:

1. Central Registry: All server dependencies are declared in src/mcp_tools.py:

   DEPENDENCIES: dict[str, object] = {
       "postmark_api_key": api_key,
       "sender_email": from_email,
       # Add new dependencies here ↓
       # "weather_api_key": os.getenv("WEATHER_API_KEY"),
   }
   

2. Signature-Based Injection: Only dependencies that appear in the function signature are injected - no hidden behavior.

Adding a New Action (< 60 seconds)

Step 1: Write the Action

Create src/actions/my_feature.py:

"""
My feature action implementation.
"""

import logging
from typing import Any

logger = logging.getLogger(__name__)


async def my_feature_action(
    user_param1: str,
    user_param2: int,
    postmark_api_key: str,    # Only injected if you need it
    sender_email: str,        # Only injected if you need it
) -> Any:
    """
    Description of what this action does.
    
    Args:
        user_param1: User-provided parameter
        user_param2: Another user-provided parameter
        postmark_api_key: Postmark API key (injected)
        sender_email: Sender email (injected)
        
    Returns:
        Result of the action
    """
    logger.info("My feature action called")
    
    # Your implementation here
    result = f"Processed {user_param1} with value {user_param2}"
    
    logger.info("My feature action completed")
    return result

Step 2: Add New Dependencies (if needed)

If your action needs additional services (like a weather API key), add them to the DEPENDENCIES registry in src/mcp_tools.py:

DEPENDENCIES: dict[str, object] = {
    "postmark_api_key": api_key,
    "sender_email": from_email,
    "weather_api_key": os.getenv("WEATHER_API_KEY"),  # ← Add this
}

Step 3: Restart the Server

That's it! The action is automatically registered as my_feature_tool.

Action Examples

Simple Action (No Dependencies):

async def status_action() -> dict:
    """Get server status - needs no external dependencies."""
    return {"status": "ok", "version": "1.0.0"}

Action with User Parameters Only:

async def greet_user_action(name: str, greeting: str = "Hello") -> str:
    """Greet a user - no server dependencies needed."""
    return f"{greeting}, {name}!"

Action Using Server Dependencies:

async def send_notification_action(
    message: str,
    recipient: str,
    postmark_api_key: str,  # Injected because it's in DEPENDENCIES
    sender_email: str,      # Injected because it's in DEPENDENCIES
) -> str:
    """Send notification email using server dependencies."""
    # Use postmark_api_key and sender_email here
    return f"Sent '{message}' to {recipient}"

Action with Custom Dependencies:

async def fetch_weather_action(
    city: str,
    weather_api_key: str,   # Must be added to DEPENDENCIES first
) -> dict:
    """Fetch weather data using external API."""
    # Use weather_api_key to call external service
    return {"city": city, "temperature": "22°C"}

Function Requirements

Naming Convention:

• Function name must end with _action (e.g., send_email_action)
• The registered MCP tool will be named by replacing _action with _tool

Parameters:

• User parameters: Exposed to MCP clients, must be documented
• Dependency parameters: Must match names in the DEPENDENCIES registry
• Type hints: Required for all parameters
• No **kwargs: Dependencies are passed as explicit named parameters

Return Value:

• Can return any serializable type (str, dict, list, etc.)
• Return value will be sent back to the MCP client

Async Function:

• Must be an async function using async def
• Can use await for I/O operations

Auto-Discovery Process

When the server starts:

1. The register_tools() function populates the DEPENDENCIES registry
2. It scans the src/actions/ package for Python modules
3. It looks for async functions ending with _action
4. For each action, it inspects the function signature
5. It creates a wrapper that injects only the dependencies the action requests
6. It registers the wrapper as an MCP tool

Testing

# Run all tests
uv run python -m pytest tests/ -v

# Test action registration specifically
uv run python -m pytest tests/test_mcp_tools.py::TestRegisterTools -v

# Test individual actions
uv run python -m pytest tests/test_send_email_action.py -v

Dependencies

• httpx: HTTP client
• mcp[cli]: Model Context Protocol implementation
• starlette: ASGI framework for the web server
• uvicorn: ASGI server
• python-dotenv: Environment variable loading
• pydantic-settings: Configuration management

License

This project is licensed under the MIT License.