mcp-ltspice-qucs

Design RF filters and switch-mode-power EMC from spec — three FastMCP servers driving LTspice, Qucs-S, and scikit-rf. Iterate at the design-intent layer ("place a zero at 1.85 GHz", "predict conducted emissions against CISPR 32 Class B") from your terminal or AI agent.

Quick start · Tools · Workflows · Documentation

What is mcp-ltspice-qucs?

mcp-ltspice-qucs is a three-server MCP suite plus a shared contracts library, all speaking Touchstone as the cross-tool exchange format. It collapses a typical filter-design loop — hours of LTspice nudging component values, swapping SPICE models, re-running, eyeballing S21 — into an agent-driven iteration at the design intent layer.

Drive it from any MCP client. mcp-ltspice exposes 76 primary tools plus 59 namespaced aliases (filter.*, power.*, analog.*, and others). mcp-qucs-s adds native S-parameter simulation, Xyce harmonic balance, and closed-form microstrip / distributed-filter synthesis with 16 substrate presets. mcp-rf-analysis adds simulator-agnostic skrf wrappers, band databases, FCC / ETSI / 3GPP spec evaluation, and multi-radio coexistence analysis. Selected LC, Qucs-S, and Xyce paths have real-simulator integration tests. Required per-commit CI installs ngspice; the weekly self-hosted matrix executes LTspice, qucsator-RF, and Xyce instead of treating an absent backend as a pass.

What mcp-ltspice-qucs does well:

• AI-native via MCP. Three first-class Model Context Protocol servers. Any MCP agent can iterate filter topologies, sweep vendor parts, and run Monte Carlo yield analyses.

• Real simulator drivers plus fast analytical models. Drives LTspice (native or under Wine), ngspice, Qucs-S / qucsator-RF for native S-parameter simulation, and Xyce for harmonic balance. Selected analytical ladder cases are cross-checked against simulator output.

• Closed-form synthesis and optimization. LC ladders (Butterworth / Chebyshev / elliptic, all of LPF / HPF / BPF / BSF including elliptic band-transforms), Sallen-Key, MFB, Richards-Kuroda, and a complete distributed set: stepped-impedance, edge-coupled, hairpin, interdigital, and combline microstrip filters on an exact coupled-line TEM model.

• Coexistence-driven design. Victim-weighted transmission-zero placement against LTE / 5G NR / GNSS / FCC-restricted bands, a GNSS ΔC/N₀ desense model, and a closed loop that iterates filter order until the coex matrix meets a desense target.

• Circuit-file workbench and model-aware optimization. Supported LTspice ASC, SPICE, Qucs schematic, and Qucsator netlist files import into a connectivity-preserving CircuitDocument 1.0 or return a complete unsupported-construct report. Component search enforces package, availability, ratings, Q/SRF, bias, temperature, and tolerance. Generic IR optimization preserves topology, evaluates corners/yield, instantiates exact selected models, and can require an independent final simulator before reporting simulator_validated.

• CISPR-aware. Conducted and radiated emission prediction against CISPR 22 / 32 and FCC Part 15 limits, anchored to closed-form references, before you build.

Related MCP server: SPICEBridge

Quick start

Install

git clone https://github.com/RFingAdam/mcp-ltspice-qucs.git
cd mcp-ltspice-qucs
uv sync --all-packages
uv run pytest -q                  # simulator-gated tests skip when tools are absent
uv run python examples/basic_lpf/design.py

See docs/installation.md for ngspice / LTspice / Qucs-S external-tool setup. The general circuit workbench guide documents file-format boundaries, backend adapters, tolerance policies, component search, and generic optimization.

Wire it into your MCP client

The repository includes a tested Codex project configuration and Claude Code project configuration. Trust the repository in the client, then inspect the three connected servers.

Claude Code:

claude mcp list

Then ask your assistant:

"Synthesize a 5th-order Butterworth LPF at fc = 1 GHz, swap in Coilcraft 0402HP and Murata GJM C0G parts at 5% tolerance, and report yield."

The agent calls synthesize_lc_filter, substitute_real_components, and monte_carlo_analysis in sequence. The bundled LPF's analytical preview reports all 5 spec criteria passing at 99% yield using catalog-snapped ideal values; verify the realized circuit in SPICE before treating that number as production evidence.

Tools

mcp-ltspice-qucs ships three MCP servers with 140 primary tools (199 registrations when the 59 deprecated mcp-ltspice aliases are included):

The underscore-separated names are canonical. The categorised dotted aliases (filter.*, power.*, analog.*, digital.*, vendor.*, sim.*) are deprecated compatibility names scheduled for removal in 1.0. Full reference in docs/tool-catalog.md + docs/tools/ (one page per server).

What it solves

Five worked examples ship under examples/: basic_lpf, buck_smps, emc_compliance, filter_compare, opamp_filter.

Workflows

mcp-ltspice-qucs fits in the following eng-mcp-suite workflow bundles:

• rf-design — closed-form trans-line synthesis (lineforge) + wire-antenna MoM (mcp-nec2-antenna) + circuit/filter sim (this server).

• coexistence-review — multi-radio band picking + filter design against CISPR limits, fed into PCB layout review (mcp-pcb-emcopilot).

See the suite manifest for the full list of sibling MCPs and bundle definitions.

Scope and related MCP servers

This suite is circuit-level + filter-synthesis focused. Deliberately stops at the antenna port and at the schematic-to-layout boundary. For:

• Antenna design → mcp-nec2-antenna (wire / MoM) or mcp-openems (FDTD).

• PCB-level EMC / SI / PI → mcp-pcb-emcopilot.

• Regulatory standards lookup → mcp-emc-regulations.

• Physical-layer testing on real hardware → a hardware-DUT MCP.

See docs/related-mcp-servers.md for the full boundary statement, decision flow, and cross-MCP workflow examples.

Documentation

• Getting started — install through first call.

• Tool catalog — all 140 primary tools, per-server pages under docs/tools/.

• Backend matrix — runtime readiness and CI validation tiers.

• Migration guide — canonical names, error semantics, jobs, and numerical changes.

• Usage example — practical end-to-end walkthrough.

• Architecture — interop contract between servers.

• Suite architecture — how this MCP fits in eng-mcp-suite.

• Changelog

Part of eng-mcp-suite

This MCP server is part of

An open umbrella for engineering MCP servers across RF, EMC, PCB, signal integrity, EM simulation, and lab test. Same brand, same docs structure, designed to compose. See the full catalog or jump to a sibling:

Contributing

Contributions are welcome.

1. Pick a GitHub issue.

2. Fork + branch (feature/your-thing or fix/your-bug).

3. Run the local check suite:

   uv sync --all-packages
   uv run pytest -q
   uv run ruff check . && uv run ruff format --check .

4. Open a PR — link the issue, request review.

Full contributor guide in CONTRIBUTING.md.

License & changelog

AGPL-3.0-or-later; per-release changes in CHANGELOG.md (Keep a Changelog format). Relicensed from Apache-2.0 in v0.4.0 to align with the eng-mcp-suite toolkit-wide AGPL move. Underlying Qucs-S (GPL), LTspice (proprietary), and scikit-rf (BSD) are runtime-invoked dependencies, not redistributed by these wrappers.

Commercial licensing

This project is licensed under AGPL-3.0-or-later. A commercial license — for embedding in a closed-source product, hosting as a paid service without AGPL's share-back obligations, or proprietary redistribution — is available on a case-by-case basis. See eng-mcp-suite's licensing policy or open an issue and tag @RFingAdam.

Acknowledgments

• LTspice — Analog Devices' SPICE simulator.

• Qucs-S — Quite Universal Circuit Simulator with SPICE-compatible kernels.

• scikit-rf — Touchstone and S-parameter library underneath the analysis layer.

• The MCP working group — for the Model Context Protocol specification.

Part of eng-mcp-suite — built for RF engineers, EMC labs, and AI agents.