Claude Code Setup

mcltspice communicates over standard MCP stdio transport. The examples below show the three main ways to configure it.

Add to Claude Code

From PyPI

The quickest option. This pulls the latest published version from PyPI and runs it with uvx:

claude mcp add mcltspice -- uvx mcltspice

If you need to pin a specific version:

claude mcp add mcltspice -- uvx mcltspice==2026.2.10

Local development

For working on mcltspice itself, point at your local checkout:

claude mcp add mcltspice -- uv run --directory /path/to/mcltspice mcltspice

This uses uv run to resolve dependencies from the local pyproject.toml and run the entry point. Changes to the source take effect on the next server restart.

Manual .mcp.json

Create or edit .mcp.json in your project root (or ~/.mcp.json for global scope):

{
  "mcpServers": {
    "mcltspice": {
      "command": "uvx",
      "args": ["mcltspice"],
      "env": {
        "LTSPICE_DIR": "/home/you/ltspice/extracted/ltspice"
      }
    }
  }
}

The env block is optional. Include it only if your LTspice files are not at the default path.

For local development, swap the command:

{
  "mcpServers": {
    "mcltspice": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/mcltspice", "mcltspice"]
    }
  }
}

Other MCP clients

Any MCP client that supports stdio transport can use mcltspice. The generic configuration is:

Field	Value
Transport	stdio
Command	uvx
Arguments	["mcltspice"]
Environment	LTSPICE_DIR (optional)

The server reads from stdin and writes to stdout using JSON-RPC over the MCP protocol. No HTTP server, no ports to configure.

Note

mcltspice uses stdin/stdout for MCP transport. It never prints diagnostics to stdout --- any startup messages go to stderr to keep the protocol stream clean.

Passing environment variables

If your LTspice installation is not at the default path, set LTSPICE_DIR in whichever way your client supports:

• Claude Code CLI: Pass it through the env field in .mcp.json (shown above).
• Shell: export LTSPICE_DIR=/path/to/ltspice before launching the client.
• Docker: Add -e LTSPICE_DIR=/path/to/ltspice to your docker run command.

Verify the connection

After adding the server, ask your MCP client to call the check_installation tool:

check_installation()

If the server is connected and LTspice is found, you will get a status report confirming the Wine version, LTspice binary path, and library availability. If anything is missing, see Prerequisites.