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MCP Calculator Server

by kumartheashwani

Backend/ServersCalculatorREST APISmitheryJSON-RPC

This is a Model Context Protocol (MCP) server implementation with a basic calculator tool. It provides arithmetic operations through a REST API and can be deployed in Smithery.

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MCP Calculator Server

A Model Context Protocol (MCP) server implementation with a basic calculator tool. This server can be deployed in Smithery and provides arithmetic operations through a REST API.

Features

  • Basic arithmetic operations (add, subtract, multiply, divide)
  • MCP-compliant API endpoints
  • JSON schema validation
  • Error handling
  • Multiple communication modes (HTTP, WebSocket, stdio)
  • Specialized entry points for different deployment scenarios

Installation

  1. Create a virtual environment (recommended):
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate
  1. Install dependencies:
pip install -r requirements.txt

Running the Server

HTTP Mode (Recommended for Production & Containers)

Run the server in pure HTTP mode using uvicorn directly:

# Set environment variable to ensure only HTTP mode runs
export MCP_HTTP_MODE=1  # On Windows: set MCP_HTTP_MODE=1
uvicorn server:app --host 0.0.0.0 --port 8000

Or use the provided script:

# On Unix/Linux/Mac
./start-container.sh

# On Windows
start-container.bat

This mode is recommended for:

  • Production deployments
  • Container environments
  • Any scenario where reliable HTTP endpoints are required

Smithery Mode (Local Tool Integration)

For Smithery integration as a local tool, use the stdio mode:

# Set environment variable to ensure only stdio mode runs
export MCP_STDIO_MODE=1  # On Windows: set MCP_STDIO_MODE=1
python server.py

Or use the provided convenience scripts:

# On Unix/Linux/Mac
./start-smithery.sh

# On Windows
start-smithery.bat

This mode is specifically designed for Smithery's local tool integration and communicates via standard input/output.

IMPORTANT: Do NOT use python server.py without setting environment variables as it starts both HTTP and stdio modes simultaneously, which can cause conflicts or timeouts.

Dual Mode (Development Only)

For development and testing both interfaces simultaneously:

# No environment variables set - runs both modes
python server.py

This starts both the HTTP server and stdio handler simultaneously, but may exit prematurely if stdin is closed. This mode is not recommended for production or Smithery integration.

API Endpoints

Standard Endpoints

  • GET /health: Health check endpoint
  • GET /tools: List available tools and their schemas
  • POST /: JSON-RPC endpoint for MCP protocol
  • WebSocket at /: WebSocket endpoint for MCP protocol

Smithery Integration Endpoints

  • POST /mcp: Dedicated MCP-compatible JSON-RPC endpoint for Smithery integration
  • WebSocket at /mcp: Dedicated MCP-compatible WebSocket endpoint for Smithery integration

These dedicated MCP endpoints are specifically designed for Smithery integration and automatically handle initialization and tool listing without requiring explicit initialization steps.

Using the Calculator Tool

REST API

Example request to the /tools endpoint:

curl -X GET http://localhost:8000/tools

JSON-RPC (HTTP)

Example request to the JSON-RPC endpoint:

curl -X POST http://localhost:8000/ \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "method": "execute", "params": {"function_calls": [{"name": "calculator", "parameters": {"operation": "add", "numbers": [1, 2, 3, 4]}}]}, "id": 1}'

Available operations:

  • add: Adds all numbers
  • subtract: Subtracts subsequent numbers from the first number
  • multiply: Multiplies all numbers
  • divide: Divides the first number by all subsequent numbers

Error Handling

The server provides clear error messages for:

  • Invalid operations
  • Division by zero
  • Insufficient number of operands
  • Invalid parameter types
  • JSON-RPC protocol errors

Deployment

Docker Container

Build and run the Docker container:

docker build -t mcp-calculator-server .
docker run -p 8000:8000 mcp-calculator-server

The container uses uvicorn directly to ensure the HTTP server starts reliably with proper signal handling, making the API endpoints accessible at http://localhost:8000.

Smithery Integration

Local Tool Integration (stdio mode)

For Smithery integration as a local tool, you must use stdio mode with the required logging configuration:

# Set environment variables for stdio mode and logging
export MCP_STDIO_MODE=1  # On Windows: set MCP_STDIO_MODE=1
export LOGGING_CONFIG=stdio  # On Windows: set LOGGING_CONFIG=stdio

# Run the server
python server.py

Or use the provided convenience scripts:

# On Unix/Linux/Mac
./start-smithery.sh

# On Windows
start-smithery.bat
Docker Container for Smithery Integration

For Smithery integration in a container, use the dedicated Smithery Dockerfile:

# Build the Smithery-specific container
docker build -t mcp-calculator-smithery -f Dockerfile.smithery .

# Run the container with stdio mode
docker run -i -e MCP_STDIO_MODE=1 -e LOGGING_CONFIG=stdio mcp-calculator-smithery

Or use the provided convenience scripts:

# On Unix/Linux/Mac
./run-smithery-container.sh

# On Windows
run-smithery-container.bat

This container is specifically configured for Smithery integration and runs in stdio mode with the required logging configuration.

Smithery Configuration

Configure Smithery to use the server as a local tool:

{
  "name": "calculator",
  "description": "A basic calculator that can perform arithmetic operations",
  "command": ["python", "server.py"],
  "env": {
    "MCP_STDIO_MODE": "1",
    "LOGGING_CONFIG": "stdio"
  },
  "type": "local"
}

This configuration ensures the server communicates via stdio when run by Smithery as a local tool and properly configures the logging system.

IMPORTANT: For local tool integration, you must use stdio mode (MCP_STDIO_MODE=1) with the LOGGING_CONFIG environment variable. HTTP mode will not work for local tool integration.

Remote Tool Integration (HTTP mode)

For Smithery integration as a remote tool (e.g., in a container), use HTTP mode with the dedicated MCP endpoint:

{
  "name": "calculator",
  "description": "A basic calculator that can perform arithmetic operations",
  "url": "http://your-container-host:8000/mcp",
  "type": "remote"
}

This configuration ensures Smithery can access the tool's API endpoints over HTTP using the dedicated MCP-compatible endpoint.

For the most reliable operation in container environments, use uvicorn directly in your deployment configuration:

{
  "name": "calculator",
  "description": "A basic calculator that can perform arithmetic operations",
  "command": ["uvicorn", "server:app", "--host", "0.0.0.0", "--port", "8000"],
  "env": {
    "MCP_HTTP_MODE": "1"
  },
  "type": "remote"
}

This ensures proper signal handling and more reliable startup in container environments.