Circuitarium MCP

Local electronics tools for MCP-capable assistants, with support for CRUMB save files and Logisim-evolution projects.

Circuitarium lets an MCP host inspect circuit files without pretending that static analysis is a running simulator. It can trace CRUMB nets, build BOMs, run electrical rule checks, analyze Logisim projects, and optionally ask Logisim-evolution to produce truth tables or run test vectors.

Release 0.3.1 includes 22 tools, nine read-only Resources, and four workflow Prompts. The server is model-neutral: Codex, Claude Code/Desktop, VS Code, LM Studio, Jan, or another local MCP host supplies the model and launches Circuitarium over stdio. Circuitarium itself needs no OpenAI, Anthropic, or local-model API key.

Quick start

You need:

• Node.js 22 or newer;
• an MCP client that can launch a local stdio server; and
• a dedicated folder containing only the circuit files you want the client to access.

Windows, macOS, and Linux are covered by CI. CRUMB analysis and the static Logisim tools need neither simulator nor Java.

To install and start the local stdio server from a terminal:

npx -y circuitarium-mcp@0.3.1

In an interactive terminal this prints a short status panel. In normal use, your MCP client runs the same command and keeps the server connected over stdio.

1. Add Circuitarium to your MCP client

Most clients ask for the same command, arguments, and environment variable:

Command: npx
Arguments: -y circuitarium-mcp@0.3.1
Environment:
  CIRCUITARIUM_MCP_ROOT=/absolute/path/to/circuit-workspace

The first launch can take longer while npm downloads the package. Later starts normally use npm's cache.

Replace the path with the smallest folder that should contain the .cru, .circ, .vec, and .txt files available to the model. Do not point it at your home directory or a drive root.

Copyable configurations are available for:

• Codex
• Claude Code
• VS Code
• LM Studio
• Jan

See the client setup guide for platform-specific examples and local-model guidance. The starter workspace recipe copies one synthetic CRUMB fixture plus the full-adder Logisim project into an isolated folder, so a first test does not require access to the rest of a source checkout. Restart or reload the client after adding the server.

Claude Desktop users can instead download circuitarium-mcp-0.3.1.mcpb directly and open it as a local bundle. The installer asks for a circuit workspace and offers optional Logisim JAR and Java settings. The release page also includes checksums and the matching npm tarball.

2. Try a circuit with no simulator installed

Paste this into the connected client:

Use Circuitarium. Call electronics_capabilities. Create the built-in breadboard-led fixture as demo/first-led.cru without overwriting anything, analyze it, and run crumb_check_design. Explain which findings are static inferences rather than simulation results.

Your client may ask you to approve creation of the synthetic file. The tool refuses to overwrite an existing path; on a repeat run, analyze the existing file or choose a new name.

A healthy connection creates a small synthetic file, recognizes its breadboard and LED, and reports two floating-terminal warnings. The fixture is independently authored and safe to redistribute; it is not a CRUMB asset.

3. Check the launcher from a terminal

These commands verify the published launcher without opening a server session:

npx -y circuitarium-mcp@0.3.1 --help
npx -y circuitarium-mcp@0.3.1 --version
npx -y circuitarium-mcp@0.3.1 doctor --smoke

If the bare npx -y circuitarium-mcp@0.3.1 command appears to wait, the server is working as designed: it is waiting for an MCP host on stdin. Press Ctrl+C and let the host launch the command itself.

Watch the terminal demo to see the source-checkout command runner inspect a synthetic fixture, build its BOM, and export its netlist. The public package exposes the MCP server, help, version, and doctor commands shown above.

Watch the MCP Inspector demo to see the server running in an independent MCP client, or read the reproducible 22-tool host verification and its sanitized evidence report.

What you can do

CRUMBLE—Circuit Representation & Universal Model Bridge for Laboratory Electronics—is the unofficial CRUMB-specific integration inside Circuitarium. The simulator-neutral tools keep CRUMB-specific assumptions out of future adapters.

The current surface breaks down into three neutral electronics_* tools, thirteen crumb_* tools, and six logisim_* tools. All tool results use the electronics.mcp/0.2 result contract, independent of the package version.

Static analysis versus runtime execution

Compatibility and honest limits

CRUMB electrical rule checks operate on inferred net connectivity and saved component values. They can find supply shorts, an LED placed directly across both rails of one recognized supply, a directly connected resistor whose saved values imply excessive dissipation, and selected floating terminals or IC power pins. They do not trace series paths, prove polarity, calculate general circuit behavior, or certify a physical build.

[!WARNING] Circuitarium is experimental educational software, not a safety certification tool. Do not rely on its output alone for mains voltage, battery charging, medical, automotive, life-safety, high-energy, or regulatory work. Use authoritative component documentation, appropriate measurements, and qualified engineering review wherever consequences matter.

File parsing happens locally, but the MCP host may send returned data to a cloud model. Embedded firmware source is omitted by default, and binary EEPROM contents are never returned, but you should still use a narrow workspace with no secrets. Read the security policy for the full trust model.

Optional Logisim runtime

The three static Logisim tools work without Java. To enable component statistics, truth tables, and test vectors:

1. Install Java 21 or newer.
2. Download the official logisim-evolution-4.1.0-all.jar.
3. Add the JAR path to the MCP host configuration.

CIRCUITARIUM_LOGISIM_JAR=/absolute/path/to/logisim-evolution-4.1.0-all.jar
CIRCUITARIUM_JAVA=java