rftools.io Now Speaks MCP: 197 Calculators for AI Agents

What Is MCP and Why Should You Care?

The Model Context Protocol (MCP) is an open standard that lets AI assistants call external tools. Think of it as a USB port for AI — any tool that speaks MCP can plug into any AI assistant that supports it.

Claude Desktop, Claude Code, Cursor, and a growing list of AI-powered development tools all support MCP. When you add an MCP server, the AI gains new capabilities. In our case: 197 RF and electronics calculators, runnable with a single function call.

Instead of the AI trying to remember formulas (and sometimes getting them wrong), it calls the same validated calculator code that runs on rftools.io.

Getting Started

Install via npm

The fastest way to try it:

npx rftools-mcp

This starts the MCP server locally. AI tools connect to it over stdio.

Claude Desktop Setup

Add this to your claude_desktop_config.json (found in ~/Library/Application Support/Claude/ on macOS or %APPDATA%\Claude\ on Windows):

{
  "mcpServers": {
    "rftools": {
      "command": "npx",
      "args": ["-y", "rftools-mcp"]
    }
  }
}

Restart Claude Desktop and you're done. Claude now has access to every calculator on rftools.io.

Claude Code Setup

claude mcp add rftools-mcp -- npx -y rftools-mcp

One command. That's it.

Three Tools, 197 Calculators

The MCP server exposes three tools:

list_calculators

Browse all available calculators, optionally filtered by category. There are 13 categories: RF, PCB, Power, Signal, Antenna, General, Motor, Protocol, EMC, Thermal, Sensor, Unit Conversion, and Audio.

Example prompt: *"List all antenna calculators"*

get_calculator_info

Get the full specification of any calculator — inputs with units and defaults, outputs, and the formula used. This is how the AI knows what parameters to provide.

Example prompt: *"What inputs does the microstrip impedance calculator need?"*

run_calculation

Run a calculator with specific inputs and get results with units. Every response includes a link back to rftools.io where you can see the interactive version.

Example prompt: *"Calculate microstrip impedance for a 0.3mm trace on 0.2mm Rogers RO4003C (Er=3.55) with 1oz copper"*

Real-World Example: Designing a Receiver Front-End

Here's a conversation that would be painful to do manually but takes seconds with the MCP server:

You: I'm designing a 2.4 GHz receiver. The antenna connects through a 50-ohm microstrip to an LNA. My PCB is 1.6mm FR4. What trace width do I need for 50 ohms, and what's my link budget for a 100m range with 0 dBm transmit power?

The AI calls run_calculation twice:

1. Microstrip impedance — iterates trace width to find the 50-ohm match (~2.9mm on 1.6mm FR4)
2. RF link budget — calculates free-space path loss, received power, and link margin at 100m

You get precise, unit-correct answers in seconds, with links to the interactive calculators for further exploration.

Why Not Just Ask the AI to Do the Math?

Large language models are impressive at reasoning but unreliable at arithmetic. They might:

• Use a simplified formula that omits copper thickness corrections
• Get unit conversions wrong (mils vs mm, dBm vs watts)
• Round at the wrong step and accumulate errors
• Confidently present a wrong answer

The MCP server calls the exact same calculator code that runs on rftools.io. These are validated implementations — Hammerstad-Jensen for microstrip impedance, Friis for link budgets, exact dB/linear conversions — not LLM approximations.

What's in the Box

All 197 calculators across 13 categories:

For AI Tool Builders: llms.txt

We also publish machine-readable documentation at the well-known /llms.txt path:

• rftools.io/llms.txt — summary with API info and MCP setup instructions
• rftools.io/llms-full.txt — complete listing of all 197 calculators with inputs, outputs, units, and URLs

The llms.txt specification is an emerging standard for making websites machine-readable. If you're building an AI agent that needs RF or electronics calculations, these files give you everything you need.

Open Source

The MCP server is part of the rftools.io codebase. The calculator functions are pure TypeScript with no browser dependencies — they work identically whether called from a web browser, an MCP server, or a Node.js script.

Install it today:

npx rftools-mcp

Or add to Claude Desktop and start designing circuits with AI assistance.