BLTSpice MCP Server

bltspice_mcp

Create any LTSpice circuit using LLMs!

Converts ltspice netlist .net to ltspice .asc file format!

REALTIME LTSpice simulation and export to .csv!

Project Layout

• src/bltspice_mcp/ server source code
• tests/unit/ unit tests
• tests/integration/ integration tests
• testfiles/ copied example assets (.asc/.log/.raw/.asy/.txt/.net)
• examples/codex/ and examples/opencode/ MCP call recipes for LLM agents
• config.json server configuration
• bltspice_mcp_for_LLM.md LLM tool-calling reference

Requirements

• Python 3.11+
• LTspice installed
• Linux/macOS with Wine for Windows LTspice binary

Quick Setup

python3 -m venv .venv
. .venv/bin/activate
pip install -U pip
pip install "PyLTSpice>=6.0.1" "fastmcp>=3.4.4" "electronics-design>=0.1.4" pytest pytest-asyncio
pip install -e .

Configuration

config.json (absolute paths required):

{
  "mcp_server_name": "My PyLTSpice MCP Server",
  "mcp_server_url": "http://localhost:7543",
  "wine_path": "/usr/bin/wine",
  "ltspice_path": "/home/brosnan/.wine/drive_c/Program Files/ADI/LTspice/LTspice.exe",
  "enable_extra_tools": true,
  "timeout": 600,
  "convert_settings": {
    "ltspice_windows_path": "C:\\users\\brosnan\\AppData\\Local\\LTspice\\",
    "ltspice_wine_path": "~/.wine/drive_c/users/brosnan/AppData/Local/LTspice/",
    "custom_search_paths": ["./valid_asy/"],
    "minimum_dist": 32,
    "wire_pin_out_dist": 16,
    "grid_size": 16,
    "autoplace_iter": 12,
    "ltspice_version": 4.1
  }
}

convert_settings is optional. Each setting is optional and receives a default when omitted. Relative custom_search_paths are resolved from the server project root; Windows paths remain in Windows syntax for Wine-based conversion.

mcp_server_url supports http://, https://, and stdio://.

Run Server

Stdio transport:

. .venv/bin/activate
python -m bltspice_mcp --config /home/brosnan/bltspice_mcp/bltspice_mcp/config.json

MCP Client Config Examples

OpenCode

{
  "mcpServers": {
    "bltspice_mcp": {
      "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python",
      "args": [
        "-m",
        "bltspice_mcp",
        "--config",
        "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json"
      ]
    }
  }
}

Claude Code

{
  "mcpServers": {
    "bltspice_mcp": {
      "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python",
      "args": [
        "-m",
        "bltspice_mcp",
        "--config",
        "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json"
      ]
    }
  }
}

OpenAI Codex

{
  "mcp_servers": {
    "bltspice_mcp": {
      "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python",
      "args": [
        "-m",
        "bltspice_mcp",
        "--config",
        "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json"
      ]
    }
  }
}

Response Contract

Server statuses:

• performing LTspice operation in progress
• LTspice operation completed!
• invalid input!
• file not found!
• unsupported file type!
• simulator not configured!
• simulation failed!
• parser failed!
• LTspice operation timed out!
• internal error

Each payload includes operation. Successful responses include output, and optionally output_obj_name.

traces_to_csv via execute

Convert selected traces from a loaded RawRead object into one CSV per wave/step.

Inputs:

• object_name: name of a stored RawRead object
• trace_refs: array of trace names (any length), for example ["V(opamp_input)", "V(opamp_output)"]
• output_files:
  • string prefix/path, example ./sim_wave_ -> writes ./sim_wave_0.csv, ./sim_wave_1.csv, ...
  • or array of explicit .csv paths with one entry per wave

Example MCP call:

{"tool":"execute","arguments":{"api_name":"traces_to_csv","inputs":{"object_name":"raw","trace_refs":["V(opamp_input)","V(opamp_output)"],"output_files":"./sim_wave_"}}}

LTspice schematic conversion via execute

The following electronics-design APIs are available through execute: is_valid_ltspice_netlist_file and ltspice_netlist_to_asc.

ltspice_netlist_to_asc receives the configured convert_settings automatically. A request may include an inputs.convert_settings object to override individual values for that call. is_valid_ltspice_netlist_file only requires its filepath.

run_ltspice_to_csv.py Equivalent MCP Flow

Equivalent artifacts are included for the op-amp example workflow:

• netlist fixture: /home/brosnan/bltspice_mcp/bltspice_mcp/testfiles/opampdouble.net
• Codex recipe: /home/brosnan/bltspice_mcp/bltspice_mcp/examples/codex/run_ltspice_to_csv.md
• OpenCode recipe: /home/brosnan/bltspice_mcp/bltspice_mcp/examples/opencode/run_ltspice_to_csv.md
• integration test: /home/brosnan/bltspice_mcp/bltspice_mcp/tests/integration/test_run_ltspice_to_csv_via_mcp.py

Integration Coverage

Integration tests now include:

• Core MCP flow test (runtime_info, execute, execute_status, stop_reset)
• Mapping coverage for the checked-in PyLTSpice example-name manifest (tests/fixtures/pyltspice_example_manifest.json)
• Mapping coverage for the checked-in README example-name list in that manifest
• End-to-end run_ltspice_to_csv.py style MCP workflow for opampdouble.net

Run Tests (One By One)

. .venv/bin/activate
pytest -q tests/unit/test_responses.py
pytest -q tests/unit/test_config.py
pytest -q tests/unit/test_dispatcher.py
pytest -q tests/unit/test_session.py
pytest -q tests/integration/test_mcp_server_integration.py
pytest -q tests/integration/test_examples_via_mcp.py
pytest -q tests/integration/test_readme_examples_via_mcp.py
pytest -q tests/integration/test_run_ltspice_to_csv_via_mcp.py

Notes

• runtime_info is immediate and does not require execute_status polling.
• Server queues execute/stop_reset in FIFO per MCP session.
• execute_status polls the latest status for queued operations.
• Completion/error notifications are emitted through MCP notification channel.