CalMag MCP Server 🌱

A professional calcium and magnesium nutrient calculator that integrates with Claude Desktop. This tool helps you calculate optimal calcium and magnesium ratios for plant nutrition using the proven CalMag calculator system.

What is this?

This is an MCP (Model Context Protocol) Server - think of it as a smart plugin that connects Claude Desktop to the professional CalMag nutrient calculator at calmag.webklex.com.

What does it do?

• Calculates precise calcium and magnesium ratios for plant nutrition
• Works with 15+ fertilizer brands (Canna, BioBizz, General Hydroponics, etc.)
• Analyzes your water quality and suggests improvements
• Provides professional-grade nutrient recommendations

What is Claude Desktop?

Claude Desktop is Anthropic's desktop application that can connect to external tools like this nutrient calculator. When you install this MCP server, Claude becomes your intelligent plant nutrition assistant with access to professional nutrient calculations.

Installation & Setup

Step 1: Install Claude Desktop

1. Download Claude Desktop from claude.ai/download
2. Install and sign in with your Anthropic account

Step 2: Connect the CalMag Calculator

On macOS/Linux:

1. Open Claude Desktop
2. Click on the settings/gear icon
3. Go to "MCP Servers" or "Integrations"
4. Add a new server with these settings:
   • Name: calmag
   • Command: npx
   • Arguments: ["-y", "@_odbo_/calmag-mcp-server"]

On Windows:

1. Open Claude Desktop
2. Access Settings → MCP Servers
3. Add new server:
   • Name: calmag
   • Command: npx.cmd
   • Arguments: ["-y", "@_odbo_/calmag-mcp-server"]

Alternative JSON Configuration:

If your Claude Desktop uses a configuration file, add this to your claude_desktop_config.json:

{
  "mcpServers": {
    "calmag": {
      "command": "npx",
      "args": ["-y", "@_odbo_/calmag-mcp-server"]
    }
  }
}

Configuration file locations:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/claude/claude_desktop_config.json

Step 3: Restart Claude Desktop

Close and reopen Claude Desktop for the changes to take effect.

How to Use

Once connected, you can ask Claude to help with calcium and magnesium nutrient calculations:

Example Conversations:

"Show me available fertilizers" Claude will list all supported fertilizer brands and products.

"Calculate nutrients for my water with 150mg/L calcium and 45mg/L magnesium using Canna CalMag Agent" Claude will first show you the default calculation settings (3.29 Ca:Mg ratio, 1L volume, linear model) and ask for confirmation before calculating.

"My water analysis shows: Calcium 200mg/L, Magnesium 80mg/L, help me calculate the right nutrient mix" Claude will analyze your water and suggest the best fertilizer ratios.

Available Tools

The MCP server provides these professional tools:

🧪 calmag_get_fertilizers

What it does: Shows all available fertilizer brands and products from 15+ professional brands When to use: ALWAYS use this tool FIRST before making any nutrient calculations Key features: Complete product database, exact nutrient compositions, brand filtering

🔬 calmag_calculate_nutrients

What it does: Calculates optimal fertilizer amounts using professional CalMag algorithms When to use: After selecting fertilizer and obtaining water analysis data New defaults: Ca:Mg ratio 3.29 (industry standard), 1L volume, linear model (default)

Required information:

• Water analysis with calcium and magnesium levels (in mg/L)
• Choice of specific fertilizer product (from calmag_get_fertilizers)
• Optional: Custom Ca:Mg ratio, calculation model, additives

📊 calmag_get_models

What it does: Shows all available calculation models and their applications When to use: To understand different calculation approaches and select the best model Available models: linear (default), fumus, dynamic_ca, dynamic_mg, dynamic_ca_mg (PPP-Ca equivalent)

🧬 calmag_get_additives

What it does: Shows available calcium and magnesium additives for fine-tuning When to use: When base fertilizer calculations need supplementation Categories: Pure calcium, pure magnesium, combined Cal-Mag products

Getting Your Water Analysis

For accurate calculations, you need your water's calcium and magnesium content:

Option 1: Laboratory Test (Most Accurate)

• Send water sample to agricultural lab
• Request "plant nutrition water analysis"
• Costs $15-30, most accurate results

Option 2: Municipal Water Report (Good)

• Contact your water utility
• Request water quality report
• Usually free, updated annually

Option 3: Home Test Kit (Basic)

• Use TDS/EC meter + calcium test strips
• Convert TDS readings to mg/L
• Less accurate but immediate results

Option 4: Local Garden Center

• Many offer water testing services
• Usually $10-20 for basic analysis

Troubleshooting

"Tool not found" or "No CalMag tools available"

1. Verify Claude Desktop is closed completely
2. Check your MCP server configuration
3. Restart Claude Desktop
4. Try asking "What tools do you have available?"

"Connection failed" errors

1. Check your internet connection
2. The tool connects to calmag.webklex.com - ensure it's not blocked
3. Try restarting Claude Desktop

"Invalid fertilizer name" errors

1. Always use calmag_get_fertilizers first to see exact names
2. Copy the fertilizer name exactly as shown
3. Use quotes around fertilizer names with spaces

"Model not available" errors

1. Use calmag_get_models to see all available calculation models
2. Default model is linear (use dynamic_ca_mg for PPP-Ca equivalent)
3. Verify model name matches exactly from the models list

Need help?

• Check the Claude Desktop documentation
• Report issues at GitHub Issues

Important Notes

⚠️ Always use actual water test data - never guess or estimate calcium/magnesium levels

✅ All calculations use the professional CalMag system from calmag.webklex.com

🔗 Real-time data: Fertilizer database and calculations are fetched live from the CalMag API

🔗 Multiple calculation models: 5 different models including PPP-Ca equivalent (dynamic_ca_mg)

🔗 Attribution: Diese Berechnung erhielten wir dankenswerterweise von https://calmag.webklex.com/ - Cal Mag Rechner Copyright © 2025 by Webklex

License

MIT License - Free to use for personal and commercial plant nutrition projects.