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):
Omit the env block to use calculators only. Restart Claude Desktop after saving.
Claude Code
To add your API key:
Cursor
Add to .cursor/mcp.json in your project:
Windsurf
Add to ~/.codeium/windsurf/mcp_config.json:
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_simulationstill exists as a compatibility form that takesjobTypeandparams, 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 needsRFTOOLS_API_KEY— see Files below. submit_simulation/get_simulation_status/get_simulation_resultare the fire-and-forget primitives underneathrun_simulationand the typed tools, for a caller that wants to submit, do other work, and poll later.run_simulationis now bounded bywaitSeconds(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 laterget_simulation_status/get_simulation_resultcall 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. Passfull: truefor 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. SetrandomSeedto 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_toolsno longer carries a hand-written sentence describing each job type's parameters; it lists them as a plain array of names (params: string[]). Read asimulate_*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.
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.
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.
Parameters:
slug(required): Calculator identifierinputs(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
| Tool | jobType | What it does | Files | Time budget | Paid-only / free-lane bound |
|---|---|---|---|---|---|
simulate_antenna_sim | antenna_sim | Wire Antenna Simulator (NEC-2) | — | 1200 s | solveMode: optimize |
simulate_emi_radiated | emi_radiated | EMI Radiated Emissions Estimator | — | 240 s | — |
simulate_eye_diagram | eye_diagram | Eye Diagram from S-Parameters | 1 × .s2p .s4p | 120 s | — |
simulate_fdtd_sparam | fdtd_sparam | FDTD Transmission Line Simulator | — | 32400 s | solveMode: normal, fine |
simulate_filter_monte_carlo | filter_monte_carlo | RF Filter Monte Carlo Analysis | — | 120 s | monteCarloIterations ≤ 500 |
simulate_impedance_matching | impedance_match | Broadband Impedance Matching Synthesizer | 0–2 × .s2p | 120 s | — |
simulate_magnetics_optimizer | magnetics_optimizer | Magnetics & Transformer Design Optimizer | — | 360 s | — |
simulate_pdn_impedance | pdn_impedance | PDN Impedance Analyzer & Decoupling Capacitor Optimizer | — | 360 s | — |
simulate_radar_detection | radar_detection | Radar Detection Performance Monte Carlo | — | 300 s | — |
simulate_rf_cascade | rf_cascade | RF Cascade Budget Analyzer | 0–12 × .s2p | 180 s | — |
simulate_sat_link_budget | sat_link_budget | Satellite & Terrestrial Link Budget | — | 240 s | — |
simulate_smps_control_loop | smps_control_loop | SMPS Control Loop Stability Analyzer | — | 300 s | — |
simulate_sparam_pipeline | sparam_pipeline | S-Parameter Analysis Pipeline | 1–4 × .s1p–.s4p | 120 s | — |
The time budget is the lane's cap, not an estimate: most jobs finish in 15–120 seconds, and queue wait may add more.
list_simulation_tools
Every job type with its tool name, parameter names, file rules, time budget and free-lane bounds — all read from the same contract the tools are generated from.
submit_simulation
Submit by job type and return at once with the job id, queue position and time budget. Takes jobType, params, and inputFiles / inputPaths for file-input job types — which need an API key; set RFTOOLS_API_KEY.
get_simulation_status
Progress, stage, queue position, start and finish times for a job id.
get_simulation_result
The finished result for a job id, summarised by default, whole with full: true.
run_simulation
The compatibility form of a simulate_* call: jobType, params, optional files (which need a key, as above), waitSeconds (default 90, max 600) and full. Prefer the typed simulate_* tool for the job you want — it is the one whose schema an agent can read.
When something goes wrong
Failures are classified by HTTP status and by the service's own error kind, never by matching text: an invalid key, a spent allowance, a rate limit with its retry time, a refused parameter (with the service's own detail, unchanged), a job too large for its lane, a mode the tier does not carry, a timeout and a service fault each read differently. Polling stops at once on a 4xx, and after five failures in a row that are not.
Example Conversations
PCB Design
You: I need a 50-ohm microstrip on 1.6mm FR4 with 1oz copper. What trace width?
AI: Calls
run_calculationwith microstrip-impedance → A trace width of ~2.9mm gives you 50.2 Ω on 1.6mm FR4 (εr=4.2). View on rftools.io →
RF Link Budget
You: Will my 100mW 915 MHz LoRa link work at 2km with 3dBi antennas?
AI: Calls
run_calculationwith rf-link-budget → Received power: -72 dBm. With LoRa sensitivity at -137 dBm, you have 65 dB of link margin. Easily workable. View on rftools.io →
Power Electronics
You: Design a buck converter: 24V input, 5V output, 3A load, 500kHz switching.
AI: Calls
run_calculationwith buck-converter → Duty cycle: 20.8%, inductor: 17.4 μH, output cap: 22 μF. View on rftools.io →
All 241 Calculators
| Category | Count | Examples |
|---|---|---|
| RF & Microwave | 29 | Microstrip impedance, coplanar waveguide (CPW/GCPW), VSWR/return loss, Smith chart, link budget, noise figure cascade, radar range, free-space path loss, mixer spur |
| PCB Design | 36 | Trace width for current, controlled impedance, edge-coupled stripline pairs (symmetric, offset, embedded), differential via with stub loss, skin depth percentage, conductor-to-pad width, BGA breakout width, aperture diagonal, maximum pad diameter, effective dielectric constant, via step response, microvia current capacity, asymmetric (offset) stripline, dual stripline, broadside-coupled pair, differential pair, via calculator, crosstalk, critical trace length, fusing current, decoupling capacitor, padstack/annular ring, BGA land pad, conductor spacing, planar spiral inductor, embedded resistor, via voltage drop |
| Power Electronics | 21 | Buck converter, boost converter, flyback, LDO thermal, battery life, MOSFET dissipation, solar panel sizing |
| Signal Processing | 14 | Filter designer, ADC SNR, FFT bin resolution, PLL loop filter, BER/SNR, Johnson noise, rise time to bandwidth |
| Antenna Design | 8 | Dipole, patch, Yagi-Uda, horn, parabolic dish, loop, EIRP, beamwidth |
| General Electronics | 24 | Ohm's law, crystal PPM tolerance, op-amp gain, 555 timer, BJT bias, MOSFET operating point, Schmitt trigger, crystal load capacitance |
| Motor Control | 22 | DC motor speed, stepper, BLDC, servo, PID tuning, gear ratio, H-bridge selection, torque converter |
| Communications | 11 | UART baud rate, I2C pull-up, SPI timing, CAN bus, USB termination, RS-485, Ethernet, Modbus, LIN bus |
| EMC/EMI | 16 | Shielding effectiveness, EMI filter, ferrite bead, ESD/TVS diode, radiated emission estimate, common-mode choke |
| Thermal | 6 | Heatsink calculator, junction temperature, thermal via array, PCB trace temperature |
| Sensor Interface | 17 | NTC thermistor, RTD, thermocouple, Wheatstone bridge, load cell, photodiode, 4-20 mA loop transmitter |
| Unit Conversion | 19 | dBm↔Watts, rectangular↔polar, frequency↔wavelength, length (mm/mil/inch), AWG wire, capacitor code, temperature, inductance, data rate |
| Audio Electronics | 18 | Speaker crossover, room modes, headphone power, class-D efficiency, audio transformer, equalizer Q |
Why Use This Instead of Asking the AI to Calculate?
LLMs are unreliable at arithmetic. They may:
- Use simplified formulas that omit corrections (e.g. copper thickness in microstrip)
- Confuse units (mils vs mm, dBm vs dBW)
- Accumulate rounding errors
- Confidently present wrong answers
This MCP server calls the exact same validated calculator code that runs on rftools.io. Hammerstad-Jensen for microstrip, Friis for path loss, exact dB/linear conversions — real engineering formulas, not LLM approximations.
How It Works
Calculators are bundled as pure TypeScript functions — no API calls, no network latency, no rate limits. The AI calls the function directly and gets instant results.
Simulation tools run server-side on rftools.io infrastructure (AWS Lambda + SQS + EC2/Fargate workers). Their input schemas are generated at build time from the same parameter contract the website's forms are built from, so a contract change reaches the agent at the next release rather than through a hand-edited string. The server validates the call, uploads any files, submits the job, polls it within the wait bound while reporting progress, and returns a summarised result with a link to the whole payload.
Machine-Readable Documentation
- rftools.io/llms.txt — Summary with API info and MCP setup
- rftools.io/llms-full.txt — Complete listing of all 203 calculators with inputs, outputs, units, and URLs
Links
- Website: rftools.io
- npm: npmjs.com/package/rftools-mcp
- Blog: rftools.io/blog
- Announcement: rftools.io Now Speaks MCP
License
MIT