autocad-mcp

autocad-mcp is a local, stdio-only MCP server that drives a running AutoCAD 2026 session through Autodesk's documented ActiveX/COM API. It follows the same model as its sibling solidworks-mcp:

• It attaches to AutoCAD already running on the Windows desktop; it never starts the application.

• It exposes scoped tools, not an arbitrary AutoCAD command execution endpoint.

• COM calls are serialised, because AutoCAD's automation session is single-threaded.

• All MCP geometry input and output coordinates are in millimetres, and all angles are in degrees.

• Written DWG/DXF files are restricted to ACAD_MCP_OUTPUT_ROOT.

Units and angles

AutoCAD stores model geometry as numbers plus a drawing-unit setting. The server reads INSUNITS and converts millimetre inputs to that setting (for example, 1,000 mm becomes 1 drawing unit when INSUNITS=metres). Unitless drawings are passed through unchanged and flagged in get_active_drawing_info.

Angles cross the MCP boundary as degrees measured counter-clockwise from the positive X axis, and are converted to the radians AutoCAD's ActiveX API expects. Values that are ratios or multipliers rather than measurements — an ellipse's radius ratio, a block insertion's scale — are unitless and are not converted: a block's own geometry is already in drawing units, so scale: 1 inserts it at actual size whatever INSUNITS says.

Related MCP server: multiCAD-mcp

Requirements

• Windows with full AutoCAD 2026 installed (not AutoCAD LT)

• AutoCAD open with an active drawing before calling a tool

• Python 3.10+

Install

git clone https://github.com/limuzi013/autocad-mcp.git
cd autocad-mcp
py -3 -m venv .venv
.venv\Scripts\python.exe -m pip install .

That puts an autocad-mcp command in the environment, which is what the MCP host runs. uv works too, if you prefer it:

uv tool install --from git+https://github.com/limuzi013/autocad-mcp autocad-mcp

Claude Code / Claude Desktop

{
  "mcpServers": {
    "autocad-mcp": {
      "command": "C:\\path\\to\\.venv\\Scripts\\autocad-mcp.exe"
    }
  }
}

Codex CLI (~/.codex/config.toml)

[mcp_servers.autocad-mcp]
command = 'C:\path\to\.venv\Scripts\autocad-mcp.exe'

Use single-quoted TOML strings so backslashes survive. Restart the MCP host after editing its configuration.

An MCP host can also be pointed straight at a checkout, with nothing installed but the dependencies — server.py at the repository root exists for exactly that:

[mcp_servers.autocad-mcp]
command = 'C:\path\to\.venv\Scripts\python.exe'
args = ['C:\path\to\autocad-mcp\server.py']

solidworks-mcp needs the same three packages, so a single virtual environment can serve both servers.

Tools

Every ActiveX signature these tools call was read from the installed acax25enu.tlb by type-library reflection rather than from documentation, and the flagged-method list is checked against it (see Method flagging below).

Inspection

query_entities returns stable AutoCAD handles; use one in set_entity_layer, erase_entity, move_entity, or copy_entity to target a particular object without relying on UI selection.

Walking a space is expensive — each entity costs an Item() call plus a property read per reported field, and every one of those is a cross-process COM round trip — so the scan stops after max_scan entities (default 5,000). The reply always says what actually happened:

• total_in_space — how many entities the space holds.

• scanned — how many were actually examined.

• truncated — true when scanned < total_in_space, i.e. the scan stopped short of the end. A filter that rejected entities after a full walk is not truncation, and does not set this.

• stopped_by — "limit", "max_scan", or null when the scan ran to the end. Raising the other ceiling would not change the result.

list_layouts reports the Model tab and each paper-space tab in tab order, with the plot device and the paper size converted to millimetres. A layout whose plot device is missing cannot report a size; that layout comes back with a null width_mm rather than failing the whole listing. A layout measured in pixels has no millimetre equivalent, so paper_units is always reported alongside.

Note that space: "paper" always means the active paper space. list_layouts shows which layout that currently is, but this server does not switch layouts.

Geometry

A layer passed to a drawing tool is checked before the entity is created, so a bad layer name cannot leave new geometry sitting on the current layer while the call reports a failure. insert_block checks the block name the same way.

draw_polyline creates a lightweight polyline, which is planar by construction. Give every vertex the same z and it becomes the polyline's elevation; a varying z is refused rather than silently flattened onto z=0.

draw_arc sweeps counter-clockwise from start_angle_deg to end_angle_deg and reports the resulting sweep_deg. Equal angles — and a 360° difference, which is the same thing — describe no arc at all and are refused; use draw_circle for a full circle.

draw_ellipse takes semi-axes: the distance from the centre to the end of each axis, not the full width and height. minor_axis_mm may not exceed major_axis_mm, because AutoCAD's underlying RadiusRatio is minor/major and cannot exceed 1; swap the two and add 90 to rotation_deg for the same ellipse.

insert_block inserts a reference to a block definition that already exists in the drawing (list_blocks lists them). Layout blocks such as *Model_Space are refused, because they are the spaces themselves. Scaling is uniform.

add_linear_dimension measures between two points. aligned measures the true distance; horizontal and vertical measure the X and Y components; rotated measures along rotation_deg, which is required for — and rejected outside of — that orientation. The reply carries measurement_mm, the value AutoCAD itself computed, converted back to millimetres.

draw_point creates a point entity. AutoCAD renders points using the drawing's PDMODE/PDSIZE, so with the default PDMODE of 0 a point is a single dot.

Editing

erase_entity, move_entity, and copy_entity address one entity by handle. erase_entity reads the entity's description before deleting it, so the reply can say what was removed. move_entity takes a from/to pair — pass [0,0] and [dx,dy] to move by a displacement — and reports the displacement back in millimetres. copy_entity places the copy in the same space as the original, on top of it unless a displacement_mm is given.

Deletion is a normal AutoCAD edit and remains undoable in AutoCAD itself, but this server cannot reverse it.

set_layer_properties changes colour, lock, freeze, and visibility on an existing layer, and requires at least one of them so that a call cannot report success having done nothing. visible is AutoCAD's LayerOn (hidden but still regenerated); frozen is the stronger setting. Freezing the current layer is refused up front with an explanation, because AutoCAD rejects it with a COM error that names neither the layer nor the reason.

capture_screenshot grabs the desktop region occupied by the AutoCAD window, so the window must be restored and unobscured. The reply carries was_foreground: false when something may have been covering it, and width_px downscales the image.

Performance notes

Two costs dominate, and both are cross-process COM round trips.

Method flagging. pywin32's _FlagAsMethod resolves each name with its own GetIDsOfNames call. get_space used to flag four names on every call — including query_entities, which calls none of them. It now flags only the one method the caller is about to use, one name at a time so that an unrecognised name costs only itself rather than abandoning the rest of the list. Flagging is only ever applied to methods whose parameters are all [in]: it replaces the type-library-derived mapping with a bare dispid, which would discard the parameter descriptions a method with [out] parameters needs to return them. That is why IAcadLayout.GetPaperSize is deliberately not flagged. tools/check_flagged_methods.py checks both properties — that every flagged name exists at all, and that none of them take [out] parameters — against the installed type library, and exits non-zero when either fails.

Space lookup is not cached, on purpose. doc.ModelSpace is re-read on every call. A cached wrapper outlives what it points at: the user can close or switch the drawing from the AutoCAD UI between any two MCP calls, and a stale wrapper would then add geometry to the wrong drawing — or a dead one — while still reporting success. Nothing cheap identifies a document safely enough to key such a cache, either: names are reused by successive unsaved drawings (a new Drawing1.dwg after the first is closed), and a released COM pointer can be reused at the same address. Validating an entry would cost the round trip the cache was meant to save. A slow correct answer beats a fast wrong one when the wrong one silently edits the user's other drawing.

Safety and current scope

• save_drawing_as accepts only a relative .dwg / .dxf path and rejects paths outside ACAD_MCP_OUTPUT_ROOT; it also refuses overwrites by default. A .dxf target is written with the DXF file type passed explicitly, because Document.SaveAs otherwise saves the current DWG format under whatever name it is handed — producing a file named .dxf that no DXF reader accepts.

• open_drawing only opens existing .dwg / .dxf files.

• There is intentionally no run_command / SendCommand tool. Such a tool would let an MCP client execute arbitrary LISP, scripts, or shell-adjacent commands inside AutoCAD.

• erase_entity deletes drawing content. It is scoped to a single handle the caller must already have obtained, and cannot delete layers, blocks, or layouts.

• This version targets 2D entities, dimensions, block insertion, layer/block/ layout inspection, document lifecycle, and screenshot feedback. Hatches, plotting, layout switching, xref attachment, and 3D solids can be added as separate, tested tools.

Tests

The suite fakes the COM surface, so it runs on any machine — AutoCAD does not have to be installed, let alone running:

cd C:\path\to\autocad-mcp
$env:PYTHONPATH = "."
.\.venv\Scripts\python.exe -m unittest discover -s tests

The unit-conversion tests carry their own table of millimetres-per-unit written from the physical definitions, so a wrong factor in acad_core cannot agree with a wrong expectation in the test.

What the offline suite does and does not establish: it checks argument validation, millimetre/degree conversion, the exact values marshalled into each COM call, that a rejected argument leaves the drawing untouched, and how many round trips each call pays for. It cannot establish that AutoCAD accepts those calls. Signatures, parameter order, and enum values are verified by reflecting the installed acax25enu.tlb; behaviour that only a live session can show — how GetPaperSize marshals its [out] pair in practice, whether a layer is locked, whether a dimension style renders as expected — is not covered by these tests.

Live verification

Exercised on 2026-08-15 against a running AutoCAD 2026 (25.1s, Chinese UI) in a drawing created from the local acadiso.dwt. Each check compared what the tool reported against what the drawing actually held, read back through COM independently of the tool that wrote it — a tool reporting success proves nothing on its own.

• Millimetre conversion under a non-default INSUNITS: with the drawing set to decimetres, a 1,000 mm line measured 10 drawing units.

• draw_arc takes degrees and reaches AutoCAD in radians: a 0°–90° arc came back with StartAngle 0 and EndAngle π/2.

• draw_ellipse semi-axes: 60 × 30 produced RadiusRatio 0.5 and a 60-unit major axis.

• add_linear_dimension reports millimetres, rotated included — 30° across a 100 mm span measured 86.60254.

• copy_entity and move_entity land where the reply says they do.

• insert_block works with the trailing optional Password argument omitted.

• save_drawing_as writes a genuine DXF: the file opens 0\r\nSECTION, not a DWG signature.

• capture_screenshot returns a PNG instead of raising.

• Validation refuses zero-sweep arcs, inverted ellipse axes, a zero radius, rotation_deg outside rotated, unknown handles, and unknown blocks.

One defect surfaced and was fixed here: an unavailable plot device does not always raise from GetPaperSize, it can also return 0 × 0, which used to be reported as a zero-width sheet instead of an unknown one.

Type-library tools

Every ActiveX signature this server calls was read from the installed type library rather than from documentation or memory. The same tools are how you check the next one:

python tools\acax_probe.py iface IAcadModelSpace   # one interface's members and parameter flags
python tools\acax_probe.py find AddArc             # which interfaces expose a name
python tools\acax_probe.py enum AcSaveAsType       # an enum's real values
python tools\check_flagged_methods.py              # gate: every flagged method is all-[in]

ACAD_MCP_TYPELIB overrides the library location; otherwise the newest acax*.tlb under C:\Program Files\Common Files\Autodesk Shared is used, whatever its language suffix.

Quick smoke check

With AutoCAD open, send:

{"name":"autocad_status","arguments":{}}

Then a minimal drawing flow is:

create_new_drawing {}
create_layer {"name":"MCP-GEOMETRY", "color_aci":4, "make_current":true}
draw_polyline {"vertices_mm":[[0,0],[100,0],[100,60],[0,60]], "closed":true}
draw_circle {"center_mm":[50,30], "radius_mm":12}
draw_arc {"center_mm":[50,30], "radius_mm":20, "start_angle_deg":0, "end_angle_deg":180}
draw_ellipse {"center_mm":[50,30], "major_axis_mm":40, "minor_axis_mm":15, "rotation_deg":30}
draw_point {"point_mm":[50,30]}
draw_text {"text":"AutoCAD MCP", "insertion_point_mm":[10,70], "height_mm":5}
add_linear_dimension {"start_mm":[0,0], "end_mm":[100,0], "dimension_line_point_mm":[50,-15],
                      "orientation":"horizontal"}
zoom_extents {}
capture_screenshot {}
save_drawing_as {"path":"examples\\first-mcp-drawing.dwg"}

Then exercise inspection and editing against the handles that came back:

query_entities {"object_name":"AcDbCircle"}        // -> handles, scanned, stopped_by
list_layouts {}
set_layer_properties {"name":"MCP-GEOMETRY", "color_aci":1, "locked":true}
copy_entity {"handle":"<handle>", "displacement_mm":[150,0]}
move_entity {"handle":"<copy handle>", "from_mm":[0,0], "to_mm":[0,80]}
erase_entity {"handle":"<copy handle>"}

License

Apache License 2.0 — see LICENSE. Copyright 2026 JIALE LIU.

Use it, change it, ship it in a commercial product; that is all allowed. What the license does require, if you redistribute this or anything derived from it, is that you keep the copyright notices, pass on a copy of the NOTICE file, and state which files you changed.