brlcad-mcp rc1

Build and edit BRL-CAD geometry by describing what you want. It talks to MGED
over the libmcpcad socket.

You need a listener for it to connect to. If you would rather not compile one,
there is a prebuilt
libmcpcad build.

Install

tar xzf brlcad-mcp-rc1.tar.gz
cd brlcad-mcp-rc1

python -m venv .venv
.venv/bin/pip install -r requirements-pinned.txt
.venv/bin/pip install -e .

Use -e, since .env is read relative to the installed package.

Then put your key in .env:

OPENAI_API_KEY=sk-...
BRLCAD_PORT=5555

Run it

Start a listener, then:

.venv/bin/brlcad-mcp chat

Things to ask it

To check both halves are talking:

what objects are in this database?

Build something:

make a 50mm cube at the origin named block
put a 10mm hole through it along Z
verify block
render block from an isometric view

Give it a drawing:

/image ~/drawings/bracket.jpg model this bracket in BRL-CAD, named bracket

It reads the dimensions off the sheet and confirms them with you before it
builds anything, then renders views of the result. Correcting a number at that
point is much cheaper than rebuilding afterwards.

Some other things it handles:

find the overlaps in this model and fix them
make the hole 12mm
undo the last change

/trace shows which step is running and which tool it called, which helps when
a result surprises you. /help lists the rest.

Without an API key

The tests and the eval harness in tool mode do not need one:

.venv/bin/python -m pytest
BRLCAD_BUILD=/path/to/brlcad/build ./evals/run.sh

The harness builds models from known dimensions and checks what came out.

Notes

• The listener accepts local connections only and has no authentication. Treat
  it as a development tool rather than something to leave running on a shared
  machine.
• A model that passes its checks matches the description the agent worked from.
  Whether that description matched your drawing is a separate question, so read
  the dimensions it reports back.
• It records the assumptions it had to make. A long list usually means the
  drawing left something open, and those are the quickest things to correct.