The evidence for track H, in the shape tracks A, E, B + G and F used.
- benchmarks/tasks_v7.py: 21 tasks, DEFAULT_MATRIX = "v7"; v6 to v2 stay
addressable. Both new tasks read the synthetic plant pair and nothing
else. takeoff_roundtrip: the P&ID called schematic, every routable run's
layout length equal to the rectilinear MST of its tags, sizes and services
as drawn (a return drawn on the supply layer included), the cable metres
rounded up after the allowance, an unstated power left empty.
understand_foreign: inches over millimetres flagged, the stray entity found
by handle, two plan copies separated, five layers classified. A test breaks
each input and watches its gate fail by name.
- Five correctness checks, every number worked out by hand in its docstring;
the published A/B report is re-run over 48 checks: 26 / 48 -> 48 / 48,
zero regressed.
- scripts/smoke_understand_com.py reads the pair through the live engine -
snapshots, the DWG route, both takeoffs and a diff - and closes every
document it opens; the CHANGELOG records what it returned.
scripts/field_test_takeoff.py runs the takeoffs on a user's own files,
refuses to write inside the repository and prints no quantity by default.
- The README token table is remeasured; check_doc_numbers derives the task
count from the v7 matrix; CLAUDE.md, both READMEs, the CHANGELOG and the
spec status line say what shipped.
One reader defect found on the way: describe.tag_occurrences read a wiring
callout ("Wiring to CP-2") as a place its panel is written, so the scale
check called CP-2 ambiguous and read "Wiring to CP1" as a phantom tag CP1 -
10 tags and 45 pairs (13.3 % within 10 %) where the generator placed 11 and
55 (21.8 %). A callout is no longer a tag occurrence, the rule
network.tag_occurrences already kept; two tests failed before the fix.
The smoke works only in documents it opened from its own temporary folder,
known by full path; it attaches with GetActiveObject only (the backend's
Dispatch fallback would launch AutoCAD), checks in the same COM-thread call
that the active document is its own before each snapshot, the DWG save and
the move, closes its documents with Close(False) and re-activates the
document that was active when it started. No new ActiveX member: Documents,
Item, FullName, ActiveDocument, Activate and Close are the ones the backend
already calls. Measured on AutoCAD 2026 (25.1s): exit 0, model-space types
equal file / live / DWG, export 0.104 s, no document of the run left open.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
31 KiB
AutoCAD MCP Pro
Production-grade AutoCAD automation for AI agents. Live through COM on Windows, or headless through ezdxf anywhere — one typed contract, two engines.
Install · Tools · Engines · Evidence · Limits · Config · Changelog
Not a mockup. Every line on this sheet was drawn by the tools this server exposes — ISO layers, involute gear geometry, DIN 6885 keyway, section A-A, ISO 129 dimensions, an ISO 286 H7 bore fit, ISO 7200 title block — then rendered headlessly by view_screenshot. drawing_critique returns 0 issues on it. Rebuild it with python scripts/render_readme_showcase.py.
The same server as a P&ID drafter. pid_from_spec placed five catalogue symbols as real blocks with TAG attributes and named ports, routed four port-to-port lines with ISA-5.1 classes and line numbers in one transaction, then pid_graph read the sheet back: 5 nodes, 4 edges, 0 dangling ends, confidence_min 1.0. Rebuild it with python scripts/render_readme_pid.py.
The catalogue, authored in code. 43 ISO 10628-2 / ISA-5.1 symbols — 11 valve bodies × 6 actuators, 6 rotating machines, 4 heat exchangers, 6 parametric vessels, 7 inline items, the instrument bubble in 4 types × 5 locations, 5 line markers, 3 connectors — every one placed through pid_symbol_insert's own path. Rebuild it with python scripts/render_pid_catalog.py.
v1.5 release snapshot: 247 tools · 8 resources · 5 prompt templates · 4960 collected tests. 247 is the registered count; a default install advertises 242 over
tools/list, becauseENABLE_3Dis unset.system_aboutis the runtime authority.
Why this exists
A big MCP server is expensive to be connected to. The full catalog costs a client 83,758 tokens before it has asked for anything. Discovery mode replaces it with two tools and costs 356.
A drafter searches for FILLET, not entity_fillet. Those command names appeared in no tool name or description — df = 0 against a stock index, not badly ranked but absent. The fix was data: an authored corpus of 206 AutoCAD command names and 1439 synonym phrases covering all 247 tools. A test refuses to let a tool exist without one.
| Advertised surface | Tools seen | Idle cost |
|---|---|---|
TOOL_PROFILE=full (default) |
242 | 83,758 tokens |
TOOL_PACKS=core,settings (full profile) |
205 | 63,890 tokens |
TOOL_PACKS=core,mech (full profile) |
197 | 64,836 tokens |
TOOL_PACKS=core,arch (full profile) |
195 | 63,532 tokens |
TOOL_PACKS=core (full profile) |
183 | 57,122 tokens |
TOOL_PROFILE=lean |
65 | 22,661 tokens |
DISCOVERY_MODE=search |
2 | 356 tokens |
Note
Offline ratio estimates, not tokenizer counts, and the uncached ratio — prompt caching amortises the idle term.
benchmarks/token_suite.py --tokenizer anthropiccounts for real.
Install
pip install autocad-mcp-pro # or: uvx autocad-mcp-pro
autocad-mcp # stdio MCP server, backend auto-selected
AUTOCAD_MCP_BACKEND=ezdxf autocad-mcp # portable DXF engine, no AutoCAD needed
AUTOCAD_MCP_BACKEND=com autocad-mcp # live AutoCAD (needs the [com] extra)
| Extra | Pulls in | For |
|---|---|---|
| (none) | fastmcp, ezdxf, pydantic |
Headless DXF on any OS — no rendering |
[com] |
pywin32, Pillow |
Live AutoCAD control + window capture |
[pdf] |
matplotlib |
PDF export and headless PNG, any platform |
[full] |
everything above | Development and CI |
Note
The bare install cannot draw pixels —
ezdxf.addons.drawingimports Pillow unconditionally, so every render path needs it. Add[pdf]for images on Linux or macOS.
Wire it to an MCP client
{
"mcpServers": {
"autocad": {
"command": "autocad-mcp",
"env": {
"AUTOCAD_MCP_BACKEND": "auto",
"ALLOWED_PATHS": "C:\\Users\\you\\Documents\\AutoCAD",
"TOOL_PROFILE": "full",
"DISCOVERY_MODE": "off"
}
}
}
}
Claude Desktop, Cursor, or any stdio MCP host. For HTTP: autocad-mcp --transport http --port 8000 — loopback only unless remote HTTP is explicitly enabled and a bearer token is set.
What you get
| Area | What it does |
|---|---|
| Drawing lifecycle | create, open, save, export DXF/PDF, audit (repairs), purge, undo/redo |
| Geometry | lines, arcs, polylines, splines, hatches, trim/extend/fillet/chamfer, handle-preserving edits |
| Annotation | ISO 129 toleranced dimensions, ISO 286 fits (fit="H7"), TABLE, MLEADER, GD&T frames and datums (ISO 1101) |
| Engineering generators | involute gears (front + section A-A), DIN 6885 keyed bores, ISO A3 title block |
| Mechanical parts | one part model (segments or outline + typed features) and one view engine: front / side / top / section / detail with hidden lines, ISO 128-50 cut faces and ISO 129 dimensions; ISO 4014/4017/4032/7089/4762 fasteners, ISO 15 bearings, DIN 471/472, DIN 509, DIN 332 and ISO 3601-2 as real blocks with attributes; ISO 21920-1 surface texture, ISO 2553 welds, ISO 128-40 section lines |
| Sheet & delivery | ISO 5457 frames A4-A0 with zones and trim marks, ISO 7200 title blocks for every size, revision blocks with clouds, ISO 7573 parts lists with ISO 6433 balloons linked by XDATA, CSV/XLSX extraction, xrefs and images on both engines, real .dwg on a live seat |
| Architecture | one plan model — walls with hosted doors and windows — and one engine: L / T / X junctions resolved, openings cut, poché by material; rooms measured from the faces the walls enclose (never typed) and read back from any plan with a confidence; door / window / room schedules as real TABLEs; a furniture and sanitary catalogue at nominal sizes; structural grid, north arrow, section / level / elevation marks; exterior dimension chains; English or Turkish labels (lang="tr", decimal comma) |
| Understanding & takeoffs | drawing_understand reads a drawing somebody else made in one call — declared vs inferred units, robust extents and the outlier behind them, plan copies, each layer's discipline and service in five languages, tags, rooms; drawing_scale_check says whether a P&ID is to scale against its layout; pipe_takeoff / cable_takeoff take the topology from the P&ID and the lengths from the layout (rectilinear MST, statuses A/B/C, power never invented) into a Turkish / English / Russian workbook; drawing_diff between revisions; drawing_topology_check for dangling ends, near misses and crossings |
| P&ID | catalogue blocks with ports and tags (ISO 10628-2 / ISA-5.1), port-to-port lines with ISA-5.1 classes and line numbers, pid_graph reads any P&ID back with confidence, instrument index / line list / equipment list, pid_from_spec one-call sheets |
| Styles & standards | ISO-25 / ANSI dimension styles, ISOCP / ROMANS text styles, ISO / ANSI leader styles from authored presets; drawing_apply_standard("iso") sets all of it plus units and the mech layers in one call; changed reports only what moved |
| Discovery | search_tools ranked over an AutoCAD command and synonym corpus — FILLET, BPOLY, QSELECT, WBLOCK, OVERKILL, CHSPACE each rank #1 of the 242-tool advertised catalog |
| Batching | cad_batch runs a step list in one round trip; fields= projects 11 result-heavy tools |
| Paper space | tab lifecycle, viewports, entity_change_space (CHSPACE), page_setup_apply (ISO 216 / ANSI Y14.1 paper, ctb, scale, device — on both engines), batch_plot with every sheet size read back from its PDF's /MediaBox, drawing_export_pdf(layout=…) |
| Page setup & templates | ISO 216 / ANSI Y14.1 sheets, ctb catalog, batch_plot verified by the PDF's own /MediaBox, five bundled templates built by the server's own tools and pinned reproducible (drawing_new(template="iso_a3_mech"), iso_a1_arch, iso_a3_pid, ansi_b_mech, ansi_d_arch), save any drawing as a template (.dwt on live AutoCAD, dwt_write refused headlessly) |
| Environment | several open documents headlessly, portable layer states (ACADMCP_LAYERSTATES XRECORDs — in the file, not in AutoCAD's Layer States Manager), named views, UCS (tool coordinates stay WCS), a system-variable catalog with ranges, document properties, and on a live seat: launch/attach, preferences, an operator prompt / pick / select — where ESC is cancelled, not an error |
| Selection | window vs crossing stated back to the caller; a polygon tested against its own shape, not its bounding box |
| Boundaries | boundary_trace (BOUNDARY/BPOLY) chains loose edges into one closed polyline, arcs kept as bulges (headless) |
| Measurement | analysis_measure_entity measures what is in the drawing, by handle |
| Hatch depth | gradients, in-place edits, typed edge boundaries (headless), island styles |
| Annotation objects | WIPEOUT, REVCLOUD, MTEXT background masks (headless), text find/replace |
| 3D solids | solid_box/cylinder/extrude/revolve/boolean on live AutoCAD (ENABLE_3D=true) |
| Quality loop | drawing_preflight → drawing_plan → drawing_critique → drawing_refine → drawing_finalize (0–100 score) |
| Delivery | drawing_deliver: DXF/PDF/PNG + SHA-256 manifest + reopen-parity checks |
247 tools in 28 groups; TOOL_PACKS=core hides the nine pid_* tools, the 22 environment tools, the 14 mechanical tools, the 12 architectural tools and the two plant takeoffs (TOOL_PACKS=core,mech keeps the mechanical ones, TOOL_PACKS=core,arch the architectural ones, TOOL_PACKS=core,plant the takeoffs) from a client that needs none of them. Plus 8 resources that cost nothing in the tool budget (autocad://drawing/info, layers, blocks, entities/stats, entities/{layer_name}, system/status, pid/symbols, standards/isa51) and 5 prompt templates.
Two rules worth knowing. Every coordinate in and out of a tool is WCS on both engines — the one exception is TEXT rotation, which stays in the entity frame because a mirrored TEXT is mirror-imaged and no scalar angle expresses that. And never read vertices back and shoelace them: that loses 28.2% of the area on a semicircular edge, silently. analysis_measure_entity(handle) reads the real geometry and states its own accuracy.
The two engines
One contract across 19 modules in backends/contracts/. @capability(key, reason=…) supplies a default that refuses, and a test holds both backends' capability key sets equal. There are 27 capability keys; read system_capabilities at runtime rather than trusting the table — five of them depend on how the machine is set up.
| Capability | COM (live AutoCAD) | ezdxf (headless) |
|---|---|---|
| Live document control | ✅ | — |
| Cross-platform, no AutoCAD | — | ✅ |
| Transactions and rollback | ✅ | ✅ |
| Paper-space layouts + viewports | ✅ | ✅ |
| Viewport model-content rendering | ✅ | ✅ ᵐ (no borders) |
| Selection window / crossing / polygon | ✅ | ✅ |
| Entity area by handle | ActiveX .Area |
Analytic, bulges included |
| HATCH filled area (islands subtracted) | AutoCAD's own number | Loops walked, hatch_style reported |
| REGION / 3DSOLID area | ✅ | — ACIS is opaque to ezdxf |
| 3D solids | ✅ with ENABLE_3D=true |
— |
| DWG write | ✅ | — |
| WIPEOUT · MTEXT background colour | — verified absent, AutoCAD 2026 | ✅ |
| REVCLOUD · BPOLY · typed hatch edges | — no ActiveX member | ✅ |
| CHSPACE | — unverified on a live seat | ✅ ᶜ |
| Undo history | ✅ | opt-in — EZDXF_UNDO_DEPTH |
| TABLE and MLEADER | Native | Portable composite |
| Screenshots and PDF | Window capture | Matplotlib ᵐ |
ᵐ Needs matplotlib ([pdf]/[full]); without it png, pdf, viewport_render and handle_overlay report unsupported headlessly.
ᶜ Headless CHSPACE carries four named restrictions in its capability reason: top-view untwisted viewports only, dimensions refused unless frozen, ACIS/proxy/table refused, viewport clipping reported rather than applied.
Important
Every COM path added in v1.5 was executed against a live AutoCAD 2026. That run found four defects reading could not — the largest being that
AcadPViewporthas noViewCentermember, so the line setting it had been silently swallowed by a bareexceptsince v1.4.
Evidence
Self-measurement, produced by scripts in benchmarks/.
Correctness — every release re-proves itself
48 deterministic headless checks against the previous tag and the current tree, each in its own subprocess so a hard crash counts as a miss rather than killing the run.
| Version | Checks passing | Pass rate | Fixed | Regressed |
|---|---|---|---|---|
| v1.5.1 (baseline) | 26 / 48 | 54.2 % | — | — |
| v1.6.0-dev (this branch) | 48 / 48 | 100 % | 22 | 0 |
The twenty-two fixed rows are new capability (miss → pass). Track H adds five: scale_check_detects_schematic (the synthetic P&ID reads schematic against its layout, and a uniform 2× copy of six tags reads to scale with factor 2), pipe_takeoff_rmst_exact (all eight routable runs of the pair measure exactly the rectilinear MST of their tags), cable_takeoff_roundup (9, 17, 19 and 10 m after the 20 % allowance, and the heater's unstated power stays empty), diff_detects_known_edits (a move, a text change, an attribute change, an add and a delete — and nothing else) and topology_known_defects (a 5 mm near miss, one interior crossing, and a clean T that is neither). Track F adds four: arch_junction_l_t_x (an L corner mitres at (4100, −100) / (3900, 100), a T stem stops on the near face at (2950, 100) / (3050, 100), an X cuts all four faces, and the wall areas are 1 400 000, 1 490 000 and 2 360 000 mm² — computed by hand), arch_room_area_net (a 4 × 5 m room between 200 mm walls measures 20.00 m² in its label and its record, not the 21.84 m² its axes enclose), arch_opening_cuts_wall (both faces are interrupted across a 900 door and two jambs close it) and arch_rooms_detect_foreign (a plan of plain lines on a WALLS layer yields 20 and 15 m² at confidence 0.6, and nothing is written). Tracks B and G add seven: mech_part_roundtrip (a part read back out of its own ACADMCP_MECH XDATA equals the part drawn), mech_section_hatch_area (a 60 x ⌀40 sleeve with a ⌀20 bore cuts 1200 mm² exactly, measured out of the drawing by analysis_measure_entity), mech_iso286_on_dimension (40 H7 is +0.025 / 0 and survives the layout), mech_thread_unrepresented_is_caught (the ISO 6410 focus fires on a thread drawn as a plain circle — a gate that never fires is not a gate), std_part_iso4014_m12 (s = 18, k = 7.5, read by value), sheet_frame_iso5457_a3 (the frame runs 20,10 to 410,287 inside the 420 × 297 sheet) and bom_balloon_link (two identical bolts are one row of quantity 2, and its balloon carries the row's item number). The other six are the three P&ID checks of track A and, from track E, settings_dimstyle_iso25_values (the ISO-25 preset lands in the DIMSTYLE table with ISO 129-1's numbers), settings_layer_state_roundtrip (save → change → restore puts the layer table back, and the state survives save/reopen because it is an XRECORD in the file) and settings_pdf_mediabox_a3 (the plotted PDF's own /MediaBox reads 420 × 297). The 26 checks v1.5.1 was gated on all still pass. Against the older v1.4.0 baseline the same 26 reported 21 / 26 → 26 / 26, five fixed, zero regressed — two of those were repaired defects (fail → pass), the diameter and radius callouts, which measured the leader as geometry and dimensioned a 40 mm bore as 60 at default settings.
The task matrix — tasks that can fail
An earlier matrix scored this server 10/10, which carried no information: every task in it exercised something the server was built around. Five were added in 1.5 because they can fail, and three did while being written; 1.6 adds six more — one the P&ID reader can fail on its own, one where the PDF file, not the setter, is the witness, one where a whole mechanical sheet has to come out clean, one where a floor plan's rooms are read back off the drawing, and two where a foreign plant's P&ID and layout are read: the takeoffs against lengths computed in advance, and the one-call report against the defects planted in it.
| Task | Verified against |
|---|---|
tool_discovery |
six AutoCAD command names, each ranking #1 |
token_budget |
83,758 → 356 tokens, against a ceiling fixed in advance |
hatch_islands |
300 filled with the island, 400 ignoring it |
selection_filter |
window 1, crossing 2, bounding box 3, polygon 1 |
measure_from_handle |
139.2699 against the 100.0 a vertex shoelace gives |
pid_roundtrip |
the example sheet drawn by pid_from_spec, read back by pid_graph, which never sees the spec: 5 nodes, 4 edges, 0 dangling, confidence_min 1.0, FIC-101 wired to FCV-101 |
page_setup_truth |
ANSI B then ISO A3 landscape applied to Layout1, each plotted through batch_plot and read back from its PDF's /MediaBox: 432 × 279 then 420 × 297 mm, not the setter's return value (a fresh layout is already A3, so the B sheet is what a no-op setter cannot fake) |
mech_assembly |
a flange-coupling A3 sheet — hub with a full section, flange with its bolt-circle end view, two ISO 4014 bolts with ISO 4032 nuts, an ISO 7573 parts list read off the drawing, linked balloons, ISO 5457 frame, ISO 7200 title block — gated on drawing_critique(focus=None) returning zero issues and a finalize score of at least 90; a test drops one balloon and watches the gate fail |
arch_roundtrip |
a two-room plan — an entrance door, an interior door, two windows, a stair — drawn by arch_plan_from_spec and read back by arch_rooms_detect, which never sees the spec: each room within 0.1 % of its label and of the net floor computed by hand (4825 × 5750 and 3825 × 5750 mm), the door and window schedules listing D1, D2, W1, W2, drawing_critique(focus=None) at zero and a finalize score of at least 90; a test removes one room label and watches the gate fail |
takeoff_roundtrip |
the synthetic plant pair — a P&ID stretched 1.3× in one room and rearranged in the other, Russian supply / return words, a return drawn on the supply layer, a reducer, a segment drawn twice — read by the scale check (schematic: 21.8 % of 55 pairs within ±10 %), pipe_takeoff (every routable run's layout length equal to the rectilinear MST of its tags, sizes and services as drawn, the run to a tag the layout lacks status C) and cable_takeoff (9 / 17 / 19 / 10 m after the 20 % allowance, the heater's power left empty); a test removes the wiring callouts and watches the cable half fail by name |
understand_foreign |
the pair's layout — inches declared over millimetres, a stray line 5,000 km out, two plan copies — comes back as millimetres with an INSUNITS warning, the stray line's handle and two clusters; the P&ID's P_product piping / P_cipsupplyline / P_cipreturnline / P_ijswater / E_power classify as product / CIP supply / CIP return / ice water / electrical; a test makes the layout declare millimetres and watches the units gate fail |
Headless performance
Workloads call the same backend methods the MCP tools call, so server-side overhead is included. Numbers move with hardware; the report records the machine fingerprint. Read the next section before quoting them — this release is slower than v1.4.0 at creating entities, on purpose.
What this release is bad at
A page that only lists strengths is a page that has not been measured.
Entity creation is slower than v1.4.0. Median of three runs on one machine and interpreter: 2,000 lines 1.4× slower, the 10,000-line roundtrip 2.3× slower. Attributed — setting EZDXF_CALL_TIMEOUT=0 returns creation to v1.4.0's numbers. The cost is the per-call asyncio.wait_for wrapped around every headless call so one hung call can no longer wedge a server whose document lock is a single asyncio.Lock. Deliberate trade, documented knob, on the 1.6 roadmap. The premium quality pass went the other way — 3.7× faster.
Wave A shipped 13 tools of a planned 39. Every cut is backed by a measurement. The REGION and 2D-boolean family went because add_region() produces a REGION with zero ACIS bytes, and the greiner_hormann substitute loses 28.2% of the area on a square with one semicircular edge.
system_run_command / system_run_lisp are a guardrail, not a security boundary — the rejection message says so in those words. A 36-verb denylist refuses the obvious cases, but AutoCAD accepts hundreds of commands and DANGEROUS_COMMANDS_ENABLED=true switches it off entirely.
Path validation is per-tool, and unscoped until you scope it. With ALLOWED_PATHS empty — the default — the only positive bound is a ten-entry system-directory denylist that does not include C:/Users, /home, /root or /var. Set ALLOWED_PATHS.
Non-AutoCAD ProgIDs are unverified. CAD_PROGID changes which COM application the backend attaches to; nothing beyond the connection has been tested against BricsCAD, ZWCAD or GstarCAD.
Known limitations of the P&ID track
The router is orthogonal and blind. pid_line_draw picks auto from seven orthogonal candidates — straight, one bend, two bends through the midline, or a stub out of each port joined by three bends — by fewest bends then length (or takes direct, or the waypoints you pass), and counts the lines it crosses — crossings comes back in every result and pid_from_spec sums it — but it does not route around them. Obstacle-avoiding routing is out of 1.6; move the symbol or pass waypoints.
A foreign drawing is read at the confidence it earns, and no higher. A block this server did not place classifies by its TAG-style attribute or a keyword in its name at 0.6 with inferred ports, or at 0.3 when a line merely touches it — and a 0.3 guess can neither raise nor suppress a critique finding. On the live engine an INSERT turned off a right angle whose members ActiveX cannot measure reports an approximate box; pid_graph takes the tighter wall of that and the attribute-inclusive box on every side, but a line ending on such a body's true edge can still be reported dangling with the nearest port as the hint. Read stats.confidence_min first.
Same-file only, DXF headlessly. Off-page connectors link within one drawing; links across files are not resolved. The headless engine reads DXF; a DWG P&ID is read through the live backend. No DEXPI/Proteus export and no ISA-5.2 binary-logic symbols in this release, recorded in the spec so nobody re-derives the cut.
Known limitations of the settings track
Layer states are ours. layer_state_save writes a portable snapshot into an ACADMCP_LAYERSTATES XRECORD. It survives save/reopen on both engines and travels with the DWG/DXF; it is not an AutoCAD LAYERSTATE and does not appear in the Layer States Manager. system_capabilities reports layer_states as mode: "xrecord" for that reason.
Six of the 22 environment tools need a live seat. Preferences, launching, the operator prompts, and the five summary fields of document properties are refused headlessly with preferences / dwgprops / live_application / interactive_prompt — a refusal, not a stub. A .dwt template is the same case (dwt_write): a .dwt is a DWG container, so headlessly the template is saved as DXF. mleaderstyle_create is not such a case — ActiveX has no MLeaderStyle collection, but the ACAD_MLEADERSTYLE dictionary holds full IAcadMLeaderStyle objects, so both engines create leader styles.
A headless dimension does not re-render. dimstyle_modify reports dimensions_using_style and rerender_required: true on the ezdxf engine; the DIMENSION keeps its rendered block until it is redrawn. AutoCAD regenerates on the next regen.
Configuration
Nothing loads a .env file — export these, or set them in your MCP client's env block.
All 17 environment variables
| Variable | Default | Purpose |
|---|---|---|
AUTOCAD_MCP_BACKEND |
auto |
auto, com, or ezdxf |
CAD_PROGID |
AutoCAD.Application |
COM ProgID the live backend attaches to |
TOOL_PROFILE |
full |
lean (65 curated tools, 55 with TOOL_PACKS=core) or full |
TOOL_PACKS |
all |
Vertical packs to advertise: core,pid,settings,mech,arch,plant (core always on) |
DISCOVERY_MODE |
off |
search replaces the catalog with search_tools + call_tool |
ENABLE_3D |
false |
Expose the opt-in solid_* tools (COM) |
LOG_LEVEL |
INFO |
Python logging level |
ALLOWED_PATHS |
(empty) | Comma-separated absolute paths the server may access |
MAX_UNDO_STACK |
5 |
Maximum retained undo snapshots |
EZDXF_UNDO_DEPTH |
0 |
Headless undo history depth; 0 disables it |
MAX_DXF_BYTES |
536870912 |
Reject larger DXF input (512 MB); 0 disables |
MAX_LIST_LIMIT |
5000 |
Bound list/selection response sizes |
COM_CALL_TIMEOUT |
60 |
Per-call live AutoCAD timeout (s); 0 disables |
EZDXF_CALL_TIMEOUT |
120 |
Per-call headless timeout (s); 0 disables |
DANGEROUS_COMMANDS_ENABLED |
false |
Allow blocked commands/LISP; reported as unsafe mode |
ALLOW_REMOTE_HTTP |
false |
Permit a non-loopback HTTP bind |
MCP_AUTH_TOKEN |
(empty) | Bearer token required for remote HTTP |
Architecture
flowchart LR
A[MCP host / AI agent] --> B[FastMCP 3 server]
B --> C[Error · audit · timing · logging · capability-refusal middleware]
C --> D[Typed contract · 19 modules · 27 capabilities]
D --> E[COM backend<br/>single-STA thread]
D --> F[ezdxf backend<br/>asyncio.to_thread]
E --> G[Live AutoCAD]
F --> H[Headless DXF]
E --> I[Engineering · critique · scoring · delivery]
F --> I
The drawing at the top of this page, as tool calls
The sequence in scripts/render_readme_showcase.py, which produced the hero sheet:
drawing_new() ISO linetypes + layers bootstrapped
drawing_apply_iso_layers("mech") ISO 128 lineweights per layer
drawing_settings({units: "mm", linear_precision: 2})
gear_draw_spur_front_view( involute flanks, not a decorated circle
module=6, teeth=24, center=[135, 172],
bore_diameter=40, keyway_width=12, keyway_depth=3.3)
gear_draw_section_aa(x_offset=300, face_width=46)
dimension_linear(...) ISO 129
dimension_diameter(..., fit="H7") deviations from authored ISO 286 tables
titleblock_apply_iso_a3(title="SPUR GEAR m6 z24", material="C45E", ...)
drawing_critique(focus=None) -> [] must be empty before finalize
view_screenshot() -> PNG
The full production loop adds drawing_preflight and drawing_plan at the front, drawing_refine after the critique, and layout_create + viewport_create + drawing_deliver at the end.
Development
uv sync --locked --all-extras
uv run pytest
uv run ruff check . && uv run ruff format --check .
uv.lock pins the whole transitive graph, so this reproduces CI exactly. CI runs Linux (3.11 / 3.12), Windows (mocked-COM), plus package, Docker and MCP-registry jobs; the release gate runs the same three test lanes before anything reaches PyPI. Releases are tag-driven: git tag vX.Y.Z && git push origin vX.Y.Z.
Roadmap (1.6)
Give back the creation throughput the per-call timeout costs — arm it only for calls that can actually block. ISO 286 interference shafts r/s/t/u. HATCH boundary geometry in entity_get (1.5 measures a hatch's filled area but does not hand back its loops). REGION/3DSOLID area headlessly, which needs a modelling kernel ezdxf does not have. An allowlist of permitted AutoLISP heads, replacing the denylist — enumerating dangerous symbols does not terminate. ezdxf.recover as a fallback on drawing_open.
Features ship when their contracts and limitations are testable — not when they make a longer checklist.
Star History
Author
Umutcan Edizsalan · Mechanical engineering work at Anka-Makine · GitHub @U-C4N
Built from production drawing work, then made model-agnostic through MCP.
License
mcp-name: io.github.u-c4n/autocad-mcp