ltspice-mcp
MCP server that runs circuits in LTspice and ngspice: sweeps, Monte Carlo, .asc schematic edits, results come back as numbers
- 71 ★ on the repository
- Last commit
- GPL-3.0
Broad access
Why this level
- The run_code tool executes Python with the server's permissions and ignores the allowed-paths list
- Without a sandbox every tool reads and writes files at any path, and schematic edits change .asc files on disk
Install
- Works in
Manual install
/plugin marketplace add cognitohazard/ltspice-mcpThen /plugin install ltspice-mcp. The plugin needs uv.
Access and checks
How we reviewBroad accessThe tool can change data, run commands or handle secrets.
- The run_code tool executes Python with the server's permissions and ignores the allowed-paths list
- Without a sandbox every tool reads and writes files at any path, and schematic edits change .asc files on disk
This is third-party code. Review the repository files before installing.
What it does
ltspice-mcp connects an AI assistant to SPICE simulators. The server exposes eight tools: run a circuit or a series of runs with measurements, manage background jobs, analyze results, read schematics and models, edit .asc schematics, verify a circuit, draw an interactive chart and run Python on top of the server's own API. LTspice is the primary simulator, ngspice works without it, and QSPICE and Xyce are available for netlists. The assistant receives results as named numbers such as a phase margin, so it does not have to read waveforms by hand. Parameter sweeps, corners and Monte Carlo take one call and run as background jobs that survive a restart and can be replayed. Before writing a file the server checks for common SPICE mistakes, while the placement of parts on a schematic is left to the assistant, with no auto-router. On Windows with LTspice 26.1 or later, a person and the assistant can edit the same open schematic. Everything the tools do is also available from Python through the ltspice_mcp.api package, for optimizers, curve fits and CI checks.
Who it is for. For electronics engineers and hobbyists who design analog circuits in LTspice or ngspice and want an agent to handle runs, measurements and schematic edits.
Good fit when
- You need the gain and transistor operating region at slow and fast process corners without hand-run simulations
- An LDO schematic is measured for overshoot, settling time and phase margin under a load step
- A 500-run Monte Carlo with 1% resistors shows the share of circuits that keep the output offset within limits
- You pick a MOSFET from the LTspice library for a 12 V, 5 A switch and compare conduction loss
- A filter is open in LTspice, the output does not move, and the assistant finds the cause and fixes the schematic
Not a fit when
- You are on macOS, where the server cannot read simulation results
- You need a PCB and routing: the server covers schematics and simulation, KiCad MCP Pro handles boards
- Your circuits are digital or FPGA: the tool is aimed at SPICE simulation of analog circuits
- Several people share the server: the run_code tool executes Python with the server's own permissions
Example request
Run a 200-sample Monte Carlo on this amplifier with 1% resistors and tell me what fraction keep the output offset under 1 mVMCP
- Transport
- stdio
- Authentication
- not required
Limitations
- The author marks the project as a work in progress, so versions may break compatibility.
- macOS is not supported: the server reads .raw and .log files in a separate process with a memory limit, which has not been validated on macOS.
- Editing .asc schematics needs LTspice because the server uses its symbol libraries. Reading and checking netlists works without a simulator.
- Python 3.11 or newer is required. The plugin and the Claude Desktop extension need uv.
- Without a sandbox the tools can use any path. The allowed_paths setting limits folders but does not apply to run_code.
- The license is GPL-3.0.
How to disable. In Claude Code the plugin is removed with /plugin uninstall ltspice-mcp, and in other clients the spice entry is deleted from the MCP config. If the package was installed through uv, uv tool uninstall ltspice-mcp removes it. The .ltspice-mcp folder with job records can be deleted by hand.
FAQ
How do I connect ltspice-mcp to Claude Code?
In Claude Code the plugin takes two commands: /plugin marketplace add cognitohazard/ltspice-mcp and /plugin install ltspice-mcp. You need uv and an installed LTspice or ngspice.
Does the server work without LTspice?
Yes, ngspice is enough for simulation and analysis. LTspice is required only for editing .asc schematics because the server uses its symbol libraries.
How is it different from the MCP server built into LTspice?
The server built into LTspice 26.1 drives the program window and returns raw samples and logs. This one returns measured values and runs sweeps and Monte Carlo in the background. Both can run side by side.
Can the server run on another machine?
Yes, docs/USAGE.md has a section on running the server on another machine. The simulator has to be installed there, and access should be restricted because run_code executes code with the server's permissions.
Where does the server keep run results?
In a .ltspice-mcp folder inside the working directory, which holds job records and results. The README advises adding it to .gitignore.
Discussion
No questions or reviews yet.
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Comparison with similar tools
Cards that share the main search query, and how they differ.
| Tool | Official | Authentication | Repository stars | Main difference |
|---|---|---|---|---|
| ltspice-mcp (this card) | no | not required | 71 | |
| KiCad MCP Pro | no | not required | 212 | PCB design in KiCad, does not run SPICE simulation |
| EasyEDA API Skill | yes | 1,104 | works with EasyEDA projects through its API and runs no simulations |
README in short
The repository opens with a paragraph on goals: speed, correctness, token economy and clean schematics. Next come a quick start for Claude Code, Claude Desktop, Cursor, Codex and other clients, example prompts, a table of supported simulators and the list of eight tools. It ends with sections on configuration and the sandbox and a description of the Python API with a sweep example.