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Guides

Simple MCP Server

This example demonstrates how to build a minimal custom MCP (Model Context Protocol) server from scratch using FastMCP 2.0.

This is a great starting point for building your own custom MCP servers with business-specific tools and logic.

Running on Unikraft Cloud

To run this MCP server on Unikraft Cloud:

1. Install the CLI. Use the unikraft CLI or the legacy kraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

1. Clone the examples repository and cd into the examples/mcp-server-simple/ directory:

Code
git clone https://github.com/unikraft-cloud/examples
cd examples/mcp-server-simple/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

When done, invoke the following command to deploy this app on Unikraft Cloud:

The output shows your instance details:

In this case, the instance name is mcp-server-simple-bbdcb and the service cool-paper-b6mht7jv. They're different for each run.

For testing, you can use the example client included in this directory. First, install uv if you haven't already, then run:

Code
export MCP_SERVER_URL=https://cool-paper-b6mht7jv.fra.unikraft.app/mcp
uv run client.py

Code
Connecting to https://cool-paper-b6mht7jv.fra.unikraft.app/mcp...

--- Listing Tools ---
Name: get_weather
Description: Get current weather for a city.

Args:
    city: Name of the city

Returns:
    Weather information including temperature, conditions, and humidity

Name: get_time
Description: Get current time in a timezone.
...

You can list information about the instance by running:

When done, you can delete the instance with:

Code
kraft cloud instance remove mcp-server-simple-bbdcb

Available tools

This MCP Server provides the following tools:

• get_weather: Get simulated weather for a city
• get_time: Get current time in a timezone
• calculate: Perform basic arithmetic operations (add, subtract, multiply, divide)

Building your own tools

This example shows the basic structure of an MCP server using FastMCP. To add your own tools:

1. Define the tool using the @mcp.tool() decorator:

   • Add type hints for parameters
   • Include a docstring describing what the tool does
   • Parameters are automatically converted to JSON schema

2. Write the tool function:

   • Process the parameters
   • Return a string result (or raise an exception for errors)

3. Test locally before deploying:

   Code
   pip install -r requirements.txt
   python server.py

Example:

Code
from fastmcp import FastMCP

mcp = FastMCP("My Custom Server")

@mcp.tool()
def my_custom_tool(param1: str, param2: int) -> str:
    """Description of what this tool does.

    Args:
        param1: Description of first parameter
        param2: Description of second parameter

    Returns:
        Result description
    """
    # Your implementation here
    return f"Processed {param1} with {param2}"

if __name__ == "__main__":
    mcp.run(transport="http", host="0.0.0.0", port=8080)

Architecture

The server uses FastMCP, a high-level framework for building MCP servers that features:

• HTTP Transport: Built-in Streamable HTTP transport
• Type-Safe: Automatic JSON schema generation from Python type hints
• Simple API: Decorator-based tool definitions

This provides:

• Standard MCP protocol support
• Automatic tool schema generation
• Built-in HTTP server
• Easy deployment to any platform

Learn more

• MCP Documentation
• FastMCP documentation
• Building MCP Servers
• Unikraft Cloud Documentation
• Building Dockerfile Images with Buildkit

Use the --help option for detailed information on using Unikraft Cloud:

Or visit the CLI Reference or the legacy CLI Reference.