BricsCAD ETP Layout MCP Server

This is the same idea as the AutoCAD MCP demo you watched (https://www.youtube.com/watch?v=KQpxiXvF4cc / thepiruthvirajan/autocad-mcp-server) but pointed at BricsCAD, and specialized for ETP (Effluent Treatment Plant) General Arrangement layouts, using the retention-time rules extracted from your 10 reference drawings.

Once running, you just talk to Claude normally:

"Draw an ETP layout for 2000 m3/day, MBR scheme, at origin 0,0" "Calculate tanks for 5750 m3/day dyeing stream + 250 m3/day printing, heavy biological load" "Draw a single 41 m3 Alkalinity Feed Tank at 20,15"

...and Claude calls the tools below, which draw live into your currently open BricsCAD drawing via COM automation. No exporting/importing DWG files — it's directly controlling the running BricsCAD session, same as the video.

How it works

Claude  <--MCP-->  server.py  <--COM/pywin32-->  BricsCAD (must be running)
                       |
                       +-- tank_sizing.py    (flow -> tank volumes/footprints)
                       +-- layout_engine.py  (arranges tanks in rows)
                       +-- bricscad_com.py   (draws rectangles/text via COM)

• design_standards.py — retention times, tank depth, fixed equipment footprints. Edit this to change engineering rules.
• tank_sizing.py / layout_engine.py — pure Python, no BricsCAD needed, can be unit tested standalone.
• bricscad_com.py — the actual "connector": talks to a running BricsCAD instance over COM (pywin32), same automation model AutoCAD's MCP demo uses.
• server.py — wraps everything as MCP tools (calculate_etp_tanks, draw_etp_layout, draw_single_tank, check_bricscad_connection).

Setup (Windows only — COM automation requires it)

1. Install BricsCAD and open it with a drawing (new or existing). In BricsCAD, make sure COM/ActiveX automation isn't blocked (default install has it enabled).

2. Install Python deps:

   pip install -r requirements.txt
   

3. Find your BricsCAD COM ProgID (versions differ slightly). Open regedit, search under HKEY_CLASSES_ROOT for a key that looks like BricscadApp.AcadApplication or Bricscad.Application.<version>. If the two candidates already in bricscad_com.py don't connect, add the exact one you find to PROG_ID_CANDIDATES at the top of that file.

4. Test the connection directly (without Claude), from the same folder:

   from bricscad_com import BricscadConnection
   conn = BricscadConnection()
   print(conn.doc.Name)   # should print your open drawing's filename
   

5. Register the MCP server with your MCP client. For Claude Desktop, add to claude_desktop_config.json:

   {
     "mcpServers": {
       "bricscad-etp": {
         "command": "python",
         "args": ["C:\\path\\to\\bricscad-mcp-server\\server.py"]
       }
     }
   }
   

   Restart Claude Desktop. You should see the 4 tools show up under this server's connector icon.

6. Open BricsCAD, open/start a drawing, then just ask Claude to draw.

Tools exposed

Tool	What it does
calculate_etp_tanks	Sizing only — no drawing. Good for sanity-checking numbers first.
draw_etp_layout	Calculates AND draws the full layout live into BricsCAD.
draw_single_tank	Draws/redraws one rectangle+label — for manual tweaks after auto-layout.
check_bricscad_connection	Confirms the server can currently reach BricsCAD.

Testing sizing logic without BricsCAD or Claude

python -c "
from tank_sizing import PlantInput, calculate_tanks
tanks = calculate_tanks(PlantInput(total_flow_m3_per_day=2000, scheme='MF'))
for t in tanks:
    print(f'{t.label}: {t.volume_m3} m3 -> {t.width_m}m x {t.length_m}m')
"

Compare against your Sky Clothing (2000 m3/day, MF scheme) reference drawing's tank table before ever touching BricsCAD.

Current limitations (same as the .NET plugin version)

• Row-based bin-packing layout, not a true optimizer — matches the general flow (screener → EQ → Bio → MBR/Clarifier → RO → chemical/sludge → evaporator) but not the exact hand-tuned arrangement in your drawings.
• Fixed equipment footprints (screener, blower room, RO skid, etc.) are rough defaults — replace with your actual vendor package sizes in design_standards.py.
• No title block, dimension lines, or north arrow yet — add more COM calls (AddDimAligned, inserting your title block as a block reference) once the tank layout itself is validated.
• Deterministic engineering-rule based sizing, not an LLM-guessed layout — numbers are traceable back to the retention-time table for client-facing drawings.

bricscad-mcp