rftools-mcp

MCP server for rftools.io — 241 RF & electronics calculators + 13 server-side simulation tools for AI agents.

Give Claude, Cursor, or any MCP-compatible AI assistant access to validated engineering calculators and heavy server-side simulations. Microstrip impedance, link budgets, filter design, converter sizing, antenna patterns, and 200+ more calculators — plus NEC2 antenna simulation, FDTD, Monte Carlo, SMPS analysis, EMI estimation, and more, all callable as MCP tools.

Quick Start

Calculators work with no API key, and so do the simulation tools: without one, a job runs on the free lane. A key raises the limits — sign up at rftools.io and generate one from your dashboard. The one thing a key is required for is a file: uploading a file needs an API key; set RFTOOLS_API_KEY.

Setup

Without API key

All 241 calculators run locally with no sign-up required, and every simulation tool that takes no file still submits — on the free lane, with the free limits and the free-lane parameter bounds stated on the response.

A job type that takes a file is the exception. Uploading a file needs an API key; set RFTOOLS_API_KEY. Without one, a call carrying inputFiles or inputPaths is refused here, with that sentence, before the file is read and before any request leaves this machine.

With API key

Sign up at rftools.io and generate an API key from your dashboard. Free accounts include 5 simulation runs/month. Pro: 100/month. API tier: 10,000/month. A paid key also unlocks the modes the free lane cannot run: the antenna optimiser and the FDTD normal and fine meshes.

Claude Desktop

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

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

Omit the env block to use calculators only. Restart Claude Desktop after saving.

Claude Code

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

To add your API key:

claude mcp add rftools-mcp -e RFTOOLS_API_KEY=rfc_your_key_here -- npx -y rftools-mcp

Cursor

Add to .cursor/mcp.json in your project:

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

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

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

Tools

What changed in 2.0.0

• One typed tool per job type. Each of the 13 simulation job types now has its own simulate_<jobType> tool (e.g. simulate_impedance_matching) with a real input schema — name, type, unit, range, options and default per parameter — generated from the job type's parameter contract. run_simulation still exists as a compatibility form that takes jobType and params, but prefer the typed tool: it is the one an agent can read the schema of.
• Uploads go through this server, inline (inputFiles: [{name, content}]) or by path on this machine (inputPaths); a file-input job type needs RFTOOLS_API_KEY — see Files below.
• submit_simulation / get_simulation_status / get_simulation_result are the fire-and-forget primitives underneath run_simulation and the typed tools, for a caller that wants to submit, do other work, and poll later.
• run_simulation is now bounded by waitSeconds (default 90, maximum 600): it submits, polls, and if the job has not finished by the bound it returns the job id, status, progress and stage rather than blocking further — the job keeps running, and a later get_simulation_status / get_simulation_result call picks it up.
• Results are summarised by default — summary, warnings, provenance, every scalar value, and long series described by length and extremes rather than listed in full. Pass full: true for the whole payload.
• No defaults are posted. A simulate_* call sends only the parameters you name; it no longer fills in the contract's defaults itself. Since a sampling job type's random seed is derived from the request body, omitting a parameter and sending it at its default are the same request to the solver but not the same body, and can draw a different sample. Set randomSeed to pin a run exactly.
• Typed errors. Failures are classified by the service's errorKind, not by matching message text — see When something goes wrong below.

Breaking:

• list_simulation_tools no longer carries a hand-written sentence describing each job type's parameters; it lists them as a plain array of names (params: string[]). Read a simulate_* tool's own input schema for the type, unit, range, options and default of each parameter.
• Unknown parameter keys are now refused locally, before any request leaves this machine — the same contract the service validates against, checked here first.

Calculator tools — no API key required

list_calculators

List available calculators, optionally filtered by category.

"List all RF calculators"
"What antenna calculators are available?"
"Show me power electronics calculators"

Parameters:

• category (optional): rf, pcb, power, signal, antenna, general, motor, protocol, emc, thermal, sensor, unit-conversion, audio

get_calculator_info

Get detailed info about a calculator — inputs with units/defaults, outputs, and the formula used.

"What inputs does the microstrip impedance calculator need?"
"Show me the buck converter calculator parameters"

Parameters:

• slug (required): Calculator identifier (e.g. "microstrip-impedance")

run_calculation

Run a calculator with specific inputs. Returns results with units and a link to the interactive version on rftools.io. Runs locally — instant, no quota consumed.

"Calculate microstrip impedance for a 0.3mm trace on 0.2mm Rogers RO4003C"
"What's the link budget for a 2.4 GHz link over 500m?"
"Size a buck converter: 12V in, 3.3V out, 2A"

Parameters:

• slug (required): Calculator identifier
• inputs (required): Object with input values, e.g. {"traceWidth": 0.3, "substrateHeight": 0.2}

Simulation tools — no API key required unless the job takes a file

Server-side jobs that are too heavy for in-browser computation. Each of the 13 job types is its own tool, simulate_<name>, whose input schema is generated from that job type's parameter contract: every parameter typed, with its unit, range, options, default and any free-lane bound stated. A call is checked against that contract before anything is sent, so a wrong parameter name comes back naming the key and the keys that are accepted, and spends no quota.

Quota: Free: 5 runs/month · Pro: 100/month · API tier: 10,000/month. Without a key a job that takes no file still runs, on the free lane, and the response says which limits applied. A job that takes a file needs a key — see Files below.

Waiting: a simulate_* call submits and waits up to waitSeconds (default 90, maximum 600), polling immediately — a mode that finishes in a second costs no delay — and reporting progress to hosts that ask for it. On reaching the bound it returns the job id, status, progress and stage; the job keeps running, and get_simulation_status and get_simulation_result pick it up. waitSeconds: 0 submits and returns at once.

Results: the default is a summary — the result's summary, warnings and provenance, every scalar value, and links — with series longer than 50 points described by their length and extremes rather than listed, so a 100 kB result arrives as about 6 kB. Pass full: true for the whole payload. The link to the stored result (resultUrl) is presigned and lives 15 minutes; ask for the status again to mint a fresh one.

Repeat submissions: an identical submission inside 60 seconds returns the job already running rather than starting a second one.

Files: a file-input job type takes either inputFiles: [{name, content}] (inline text, up to 5 MB in one call) or inputPaths: ["/path/to/file.s2p"] (read from this machine). The server obtains the presigned upload, sends the file, and submits the job with the resulting key.

Uploading a file needs an API key; set RFTOOLS_API_KEY. The service refuses an anonymous upload, so this server refuses it first — locally, before the file is read and before any request is made — and says which variable to set rather than passing back a bare 401. The uploaded object is recorded against the key's account, and only that account may submit it.

The 13 job types