autocad-mcp-pro/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

AutoCAD MCP Pro is a FastMCP 3.0 server that exposes 87 tools, 6 resources, and 5 prompt templates for AutoCAD automation. (The exact tool count is reported dynamically by system_status / system_about — never hardcode it.) It runs with a dual-engine architecture: a live COM backend (Windows/AutoCAD required) and a headless ezdxf backend (works anywhere).

Running the Server

# STDIO mode (default, for MCP clients like Claude Desktop)
python server.py

# HTTP mode
fastmcp run server.py:mcp --transport http --port 8000

# Force a specific backend
AUTOCAD_MCP_BACKEND=ezdxf python server.py   # headless file ops
AUTOCAD_MCP_BACKEND=com python server.py     # live AutoCAD (Windows only)
AUTOCAD_MCP_BACKEND=auto python server.py    # auto-detect (default)

Installation

# Core (ezdxf backend only)
pip install -e .

# With COM backend (Windows + AutoCAD)
pip install -e ".[com]"

# With PDF/screenshot support via matplotlib
pip install -e ".[pdf]"

# Everything
pip install -e ".[full]"

Running Tests

pytest
pytest tests/test_specific.py::test_name   # single test
pytest -x                                   # stop on first failure

Uses pytest-asyncio for async test support.

Architecture

Dual-Backend Pattern

The server uses a strategy pattern with an abstract base:

• backends/base.py — AutoCADBackend ABC defining the full interface + shared dataclasses (EntityInfo, LayerInfo, BlockInfo, DrawingInfo, CommandResult)
• backends/ezdxf_backend.py — EzdxfBackend: file-based DXF operations using the ezdxf library. All sync ezdxf calls are wrapped with asyncio.to_thread via _async(). Transactions are implemented as full DXF snapshots on an _undo_stack.
• backends/com_backend.py — ComBackend: live AutoCAD control via pywin32 COM. All COM calls are routed through a ThreadPoolExecutor with a single thread to satisfy AutoCAD's STA (Single-Threaded Apartment) COM requirement.

Backend selection at startup (in server.py::_make_backend):

1. Check AUTOCAD_MCP_BACKEND env var
2. On Windows with auto/com: try COM first, fall back to ezdxf
3. On non-Windows: always use ezdxf

FastMCP Server Structure (server.py)

The mcp FastMCP instance is configured with:

• Lifespan (autocad_lifespan): initializes the backend singleton; stores it in ctx.lifespan_context["backend"]
• Middleware stack: ErrorHandlingMiddleware → AuditMiddleware (custom timing/audit log) → TimingMiddleware → LoggingMiddleware
• _backend(ctx) helper: retrieves the backend from lifespan context, raises ToolError if not ready

Tools are organized into 12 sections:

1. Drawing Management (11 tools): drawing_*
2. Entity Creation (13 tools): entity_create_*
3. Dimensions (5 tools): dimension_*
4. Entity Modification (10 tools): entity_move/copy/rotate/scale/mirror/offset/delete/array_*
5. Entity Query (3 tools): entity_get, entity_list, entity_delete_many
6. Layer Management (12 tools + 2 linetype_*): layer_*, linetype_list, linetype_load
7. Block Operations (7 tools): block_*
8. Analysis & Query (8 tools): analysis_*
9. View & Screenshot (5 tools — includes view_zoom_and_screenshot): view_*
10. Transactions (3 tools): transaction_begin/commit/rollback
11. System (6 tools): system_status/get_variable/set_variable/run_command/run_lisp/about
12. Engineering / Deterministic CAD (7 tools): gear_draw_*, keyway_draw_*, titleblock_apply_iso_a3, drawing_finalize

Adding a New Tool

1. Add the abstract method to AutoCADBackend in backends/base.py
2. Implement it in EzdxfBackend (backends/ezdxf_backend.py) using the _async(func) wrapper
3. Implement it in ComBackend (backends/com_backend.py) using self._com(func)
4. Register the tool in server.py with @mcp.tool(...) calling _backend(ctx).your_method(...)
5. Use _dc(result) to convert dataclass returns to dicts

Key Conventions

• Entity handles: hex strings (e.g. "1A2B"). Always returned from create/copy operations; required by all modify/query operations.
• Coordinates: drawing units (mm by default); angles in degrees, counter-clockwise from X axis.
• ACI colors: 1–255 for specific colors, 256=ByLayer, 0=ByBlock.
• COM backend only: system_run_command, system_run_lisp, and view_zoom_extents/window (view ops are no-ops in ezdxf).
• Screenshot: COM uses Win32 window capture (Pillow required); ezdxf renders via matplotlib.
• _dc(obj): converts dataclasses to dicts recursively for JSON serialization.
• Engineering layer scaffold: drawing_new auto-bootstraps standard linetypes (CENTER, HIDDEN, PHANTOM) and engineering layers (GEOMETRY, DIM, CENTER, HIDDEN, PHANTOM, HATCH, TEXT, TITLEBLOCK). Pass bootstrap=False to opt out.
• Production drawings: For real engineering output, use the engineering/ package primitives via the gear_* / keyway_* / titleblock_* MCP tools — do NOT hand-draw teeth/keyways/sections with raw entity_create_* calls. Always end with drawing_finalize for the 8-step validator.