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.

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

CIRCUITARIUM_JAVA is optional when java already resolves to Java 21 or newer. On a headless Linux machine, test-vector execution also needs a working X11 display; Xvfb is sufficient.

Use only a trusted JAR. Circuitarium verifies that it self-reports version 4.1.0, but that response does not authenticate the file or its publisher. Runtime tools may update Logisim's per-user Java preferences and are not an operating-system sandbox.

The repository includes an independently authored full-adder project and vector for a first runtime test. Circuitarium does not bundle or download Logisim-evolution. See the Logisim adapter guide for setup, Linux notes, evidence levels, and subprocess safeguards.

Typical workflows

Review a CRUMB save

1. Call electronics_capabilities.
2. Call crumb_list_projects if the path is not known. Projects include a digest when requested and within the documented file and aggregate bounds; otherwise the result explains why it was omitted.
3. Call crumb_analyze_design with view: "summary".
4. Use crumb_export_netlist, crumb_trace_net, crumb_check_design, or crumb_bom only as the question requires.

Static findings remain file-format inference. Circuitarium does not observe whether CRUMB is running or how the circuit behaves.

Verify a Logisim project

1. Call logisim_list_projects, then logisim_analyze_design.
2. Treat logisim_export_netlist as partial static evidence and review its conversion-loss markers.
3. If the optional runtime is available, select an exact circuit and call logisim_truth_table or logisim_run_test_vector.
4. Use electronics_plan_verification when a claim needs several kinds of evidence or an explicit list of remaining gaps.

Hand work to another model

Keep projectRef, projectDigest, backendId, adapterVersion, and compatibilityProfile with the handoff. The receiving model should pass the recorded digest as expectedProjectDigest on its first read. If the bytes have changed, Circuitarium returns PROJECT_STATE_CONFLICT instead of silently reusing stale conclusions.

See the cross-model handoff example.

Tool reference

The nine Resources provide capability metadata, compatibility profiles, synthetic-example metadata, electrical-review and digital-testing guidance, a neutral component-profile schema, and version-pinned component catalogs. The four user-invoked Prompts are:

• review-circuit-design
• compare-crumb-designs
• verify-logisim-design
• handoff-circuit-project

Resources and Prompts do not read a project or run a simulator by themselves. Clients that do not expose those MCP features can still use all 22 tools. The contract reference documents exact resource URIs, Prompt arguments, result envelopes, errors, output bounds, and tool schemas.

Contributing

Circuitarium is still early, and small, well-evidenced improvements are useful. Good starting points include client setup fixes, synthetic test circuits, source-cited component profiles, parser edge cases, controlled compatibility observations, and scoped roadmap work.

Before changing an adapter or public contract, read the contribution guide, architecture, and provenance policy. Questions and early design ideas belong in Discussions; reproducible bugs, scoped feature requests, and controlled interoperability evidence belong in the issue tracker.

git clone https://github.com/Craftiee/circuitarium-mcp.git
cd circuitarium-mcp
npm ci
npm run lint
npm run check

Use npm run test:coverage for behavioral changes, npm run package:check for package or launcher changes, and npm run logisim:e2e for Logisim runtime changes. The Logisim E2E test requires Java 21 and a separately supplied 4.1.0 all-JAR.

Fixtures must be small, synthetic, independently authored, and safe to redistribute. Do not submit private circuits, firmware, simulator binaries, extracted assets, or third-party circuit designs. Build a minimal synthetic reproduction instead. Report vulnerabilities through GitHub private vulnerability reporting, not a public issue. All contributors must follow the Code of Conduct.

Documentation

Privacy Policy

Circuitarium runs locally over stdio, has no telemetry, and does not send circuit files to a maintainer-controlled service. The MCP host and model provider you choose may still process tool arguments and results under their own terms. Read the complete Privacy Policy before granting a host access to a workspace.

Project status and license

Circuitarium MCP is experimental community software released under the Apache License 2.0. Version 0.3.1 is available on npm and as a GitHub release, and its metadata is listed in the official MCP Registry. For help, see SUPPORT.md. Research and teaching users can cite the project with CITATION.cff.

Circuitarium MCP, CRUMBLE, and the Logisim-evolution adapter are independent, unofficial interoperability work. They are not affiliated with, endorsed by, or sponsored by CRUMB, Logisim-evolution, or their developers. This repository contains no CRUMB or Logisim-evolution simulator code, binaries, extracted assets, logos, or bundled third-party circuit designs. Product names and marks belong to their respective owners.