symbolics-mcp

symbolics-mcp

An MCP (Model Context Protocol) server that lets LLMs evaluate Lisp expressions on a Symbolics Genera machine over TCP.

The system has two parts:

1. eval-server.lisp -- a TCP evaluation server that runs on the Genera machine
2. genera-mcp.lisp -- an MCP stdio server that runs on the host (SBCL) and bridges JSON-RPC requests to Genera over TCP

Prerequisites

• A Symbolics Genera virtual machine (e.g. via Open Genera on a Linux/Alpha host or the VLM)
• SBCL on the host machine running the virtual Genera
• Quicklisp installed in SBCL (the MCP server loads usocket and yason via Quicklisp)

Setting up the Genera side

First, copy eval-server.lisp to the Genera SYS:SITE; directory on the host filesystem:

cp eval-server.lisp /opt/symbolics/lib/sys.sct/site/eval-server.lisp

Then load it from the Genera Lisp Listener:

Load File SYS:SITE;eval-server.lisp

The file must be loaded once per boot. It does two things:

• Defines a TCP server (:mcp-server) that accepts connections, reads length-prefixed Lisp expressions, evaluates them, and returns the result, stdout, and stderr as length-prefixed fields.
• Registers the server on TCP port 8888 via tcp:add-tcp-port-for-protocol.

After loading, the server starts automatically -- there is no separate start command. It listens on port 8888 and handles each connection in its own process.

To verify it is running, you can send a test expression from the host:

echo -n '11 (+ 1 2 3 4)' | nc -w 2 192.168.11.2 8888 | cat -v

The number before the space is the byte length of the expression ((+ 1 2 3 4) = 11 bytes). If the server is working, you should see a response containing 10 (the result of the expression).

MCP configuration

Add the following to your .mcp.json (or the MCP configuration of your client), adjusting the path and IP address for your setup:

{
    "mcpServers": {
        "symbolics-genera": {
            "command": "/path/to/genera-mcp.sh",
            "env": {
                "GENERA_HOST": "192.168.11.2",
                "GENERA_PORT": "8888"
            }
        }
    }
}

Environment variables

Exposed tool

The MCP server exposes a single tool:

• eval_lisp -- Evaluate a Common Lisp / Zetalisp expression on the Genera machine and return the result. The response includes the return value, stdout, and stderr (if any).