MCP Server Sample

A sample repository demonstrating two ways to run an MCP (Model Context Protocol) server using Python: stdio (local subprocess) and HTTP/SSE (remote HTTP).

What It Does

Both servers expose a calculate_powers tool that computes the square, cube, and 4th power of a number. The HTTP server also adds a calculate_negative_powers tool, a numberpowers://info resource containing historical notes about number powers, and a powers_explanation prompt.

Project Structure

├── server.py                  # Stdio MCP server (single tool)
├── server_http.py             # HTTP/SSE MCP server (two tools + resource)
├── requirements.txt           # Python dependencies
├── numberPowers.txt           # Text file served as a resource
├── opencode.json              # opencode config for HTTP server
└── stdioMcpServerConfig.json  # opencode config template for stdio server

Prerequisites

• Python 3.10+
• An MCP-compatible client (e.g., opencode)

Setup

# Create and activate a virtual environment
python -m venv venv
source venv/bin/activate

# Install dependencies
pip install -r requirements.txt

Running the Servers

Stdio Server (server.py)

The stdio server runs as a subprocess and communicates over stdin/stdout. It exposes one tool: calculate_powers.

python server.py

HTTP/SSE Server (server_http.py)

The HTTP server runs on http://localhost:8000 and communicates over Server-Sent Events (SSE). It exposes two tools (calculate_powers, calculate_negative_powers), one resource (numberpowers://info), and one prompt (powers_explanation).

python server_http.py

The SSE endpoint is available at http://localhost:8000/sse.

Adding to opencode

Option 1: Stdio (local subprocess)

Add the following to your opencode.json in the project root:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "number-powers": {
      "type": "local",
      "command": ["python", "server.py"],
      "enabled": true
    }
  }
}

Adjust the command array to use absolute paths if needed (e.g., ["/path/to/venv/bin/python", "/path/to/server.py"]).

Option 2: HTTP/SSE (remote server)

Start the HTTP server first (python server_http.py), then add this to your opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "number-powers-http": {
      "type": "remote",
      "url": "http://localhost:8000/sse",
      "enabled": true
    }
  }
}

Applying Changes

After saving opencode.json, restart opencode for the MCP server to be available.

Available MCP Capabilities

Server	Type	Tools	Resources	Prompts
server.py	stdio	calculate_powers(number)	—	—
server_http.py	HTTP/SSE	calculate_powers(number), calculate_negative_powers(number)	numberpowers://info	powers_explanation(number)

Tool Details

calculate_powers — Accepts a number, returns its square, cube, and 4th power as a comma-separated string.

calculate_negative_powers — Accepts a number, returns its negative powers (n^-1, n^-2, n^-3) as a comma-separated string. (HTTP server only)

numberpowers://info — Returns historical notes about number powers from ancient civilizations. (HTTP server only)

Prompt Details

powers_explanation — Accepts a number and returns a prompt asking the LLM to calculate and explain all powers of that number (square, cube, 4th power, and negative powers). (HTTP server only)

Invoking Prompts in OpenCode

OpenCode supports invoking MCP prompts through the chat interface. To use the powers_explanation prompt:

1. Start the HTTP server: python server_http.py
2. In OpenCode, mention the prompt in your message, for example:

   Use the powers_explanation prompt for number 22
   

3. OpenCode will call the MCP server's prompts/get endpoint with the prompt name and arguments.

Alternatively, you can manually invoke the prompt via the MCP protocol:

{
  "method": "prompts/get",
  "params": {
    "name": "powers_explanation",
    "arguments": {
      "number": 22
    }
  }
}

License

See LICENSE.