inventor-mcp-server

Maintained continuation of NeonGlay/inventor-mcp.
The original repository has had no activity since its initial release (June 2026), and fresh
installs there fail on MCP SDK 2.x. This repo carries the full original history plus the fixes
and features that were submitted upstream as PRs and never reviewed. If the original author
returns, everything here is available to be merged back. See CHANGELOG.md.

MCP server for parametric 3D modeling in Autodesk Inventor — drive Inventor with Claude (or any MCP client) in natural language.

Build real parametric parts — flanges, shafts, nuts, brackets, sheet-metal enclosures — by talking to an AI assistant. The server wraps Inventor's COM API with high-level, millimeter-based tools and ships with battle-tested knowledge of Inventor 2026 API quirks that aren't documented anywhere else.

You:    "Build a DIN 934 M16 hex nut with proper conical chamfers"
Claude: creates sketch → hexagon → extrude → tapped M16×2 hole →
        revolve-cut chamfers → done. Fully parametric, dimensioned sketches.

Features

63 MCP tools: sketching, extrude/revolve, shell, loft, sweep, native hole features (drilled / tapped / counterbore), fillets, chamfers, circular patterns, sheet metal (named rules / Face / auto-mitered Flanges / Cut at world coordinates / Corner Round, with Flat Pattern support), parameters
Assemblies with vendor parts: import_step (keeps the files in your project folder), placement with full orientation, check_interference / measure_distance, and sweep_rotation to check a door or lock moves freely through its whole range
Assemblies (IAM): place components, ground them, constrain by origin geometry (mate / flush / angle) or drop a bolt into a hole with a single Insert constraint
execute_python power tool — run arbitrary Python against the live COM connection with a persistent namespace (escape hatch for anything not covered by dedicated tools)
Auto-reporting — every feature operation returns a volume/topology delta (Hole1 | V 23497 (-503 mm³) | F7 E14), so the AI can self-verify each step
One tool per job — 63 tools with verb_noun names: find_faces / find_edges work in a part and at any depth of an assembly, constrain takes origin geometry, faces and edges, and manage_* tools group what you do to documents, occurrences, features, parameters, constraints, materials and sheet metal rules
Protects your files — save_document saves only the active document unless asked, never a library or Content Center file; add your own paths with INVENTOR_MCP_PROTECTED or ~/.inventor-mcp/protected.txt. Deleting a component says what depends on it first, and reports what moved; replacing one reports the constraints it lost
Never hangs on a dialog — calls run with SilentOperation on a dedicated Inventor thread. A call stuck behind a modal dialog, or a long job, returns within 50 s with the dialog's title and text (read from the window list, no COM call); manage_call(wait_seconds=30) follows it — with the prints and progress() line so far — and returns the result the moment it finishes; manage_call(action="cancel") stops it
Checks before the shop does — check_manufacturability reads a sheet metal part's flat pattern: flanges too short for the V die, holes too close to a bend line, a flat that does not fit the sheet, a rule that does not match the thickness; on an assembly it finds parts with no room for the powder coat
Shop-floor outputs — export_flat_pattern gives the flat size and writes the DXF/DWG for the laser (contour, holes and bend lines on their own layers); create_drawing makes a PDF drawing (base + projected + iso views, overall dimensions, section and detail views, parts list and balloons for an assembly, or the flat pattern dimensioned with a note on every bend and a bend table); export_bom lists the assembly's parts with quantity, part number, description, material and mass (CSV for Excel / ERP); edit_properties reads and sets part number, description, stock number, material and custom properties
Real arcs in sketches — draw_closed_profile takes rounded corners ([x, y, r]) and arcs through a point, plus draw_rectangle(corner_radius), draw_slot, draw_arc and project_edges (exact edges of a body, for remodelling). Arcs go through three points, so a sketch with flipped axes can't mirror them; inspect_model warns when a curve was drawn as many short lines. draw_pattern draws grids and circles of holes / slots, offset_profile offsets loops, and check_sketch (also built into extrude's error) points at the gap that keeps a profile open
Sees its own work — capture_view returns pictures of the model (iso / front / top / … , several in one call, zoom to components, isolate them, or from any point with look_from) as images the agent can look at, with sketches hidden and the user's camera put back. A flange on the wrong side or a part floating off the frame shows at a glance
Steel frames — add_frame_members lays Content Center profiles along skeleton lines (start → end, roll, centered or at the profile origin, shortened or extended at either end) and returns a saw cut list — what Frame Generator does, which has no API. A 13-member frame takes ~35 s
Surfaces to solids — convert_surfaces_to_solid knits an imported surface model, patches the holes in the shell and closes it into a solid (or turns a closed shell into one directly), with the volume and any edges it couldn't close
Materials in bulk — manage_materials gives every matching part of an assembly a material (Content Center parts left alone), reports material and mass per part and flags Generic parts, surface-only vendor models and parts with no mass; edit_properties(mass_kg) overrides a mass
Nested assemblies — find_faces finds faces of components inside sub-assemblies (type, normal, position, diameter) in top coordinates; constrain constrains them, corrects a wrong offset sign from where the face must land, and reports any other component the constraint dragged along
Content Center and big assemblies — use_content_center browses categories → families → sizes and makes members, custom length included (a 1500 mm DIN 1026-1 U 100 in one call); place_components places dozens of components with position, orientation, name and grounding in one call
Agent-friendly Python — execute_python errors show the traceback from the agent's own lines (also in helpers defined in earlier calls), stderr is captured, and undo_on_error=True rolls back everything the call did. load_library (or ~/.inventor-mcp/startup.py) keeps helper code loaded across namespace resets. COM errors come with their name and a hint (E_INVALIDARG, RPC_E_DISCONNECTED …) instead of a localized "Exception occurred". save_document checks the path first instead of failing with E_INVALIDARG and never rewrites library or Content Center files; manage_documents clears the Part12s left by failed attempts
Several Inventors at once, across restarts — e.g. two agents on two projects (Claude Desktop runs one server for all its chats). connect(project="…ipj") reuses the Inventor that has the project, or the running one if it is free, or starts a separate one; every tool takes instance= to pick one, and each has its own call thread and execute_python namespace, so one agent's long call doesn't hold up the other. list_instances shows them. An Inventor opened by hand can't be targeted — Windows always hands out the first one — so let the server start the second. A keeper process holds the Inventors the server started, so after a restart of the client connect(project=…) gets them back
Transactions — wrap multi-step builds, roll back everything with one call
Hot reload — edit the API wrapper and reload without restarting the MCP client
Topology helpers — find edges/faces by coordinates instead of guessing indices
Parametric discipline — projected origin points, symmetry constraints, dimensioned sketches that survive parameter changes

Requirements

Windows with Autodesk Inventor (developed on Inventor 2026, also verified on Inventor 2027; older versions may need enum adjustments — see docs/inventor-api-notes.md)
Python 3.12+
pip install "mcp[cli]" pywin32 — MCP Python SDK 1.x and 2.x are both supported (2.x renamed FastMCP to MCPServer; the server detects which is installed)
An MCP client — used daily with Claude Code and Claude Desktop (several agents at once, see below)

Installation

Clone this repository:

git clone https://github.com/cenitu/inventor-mcp-server.git

Install dependencies:
```
pip install "mcp[cli]" pywin32
```
Register the server with your MCP client. For Claude Code, add to .mcp.json in your project root (see .mcp.json.example). Use the absolute path to inventor_mcp_server/server.py:
```
{
  "mcpServers": {
    "inventor": {
      "command": "python",
      "args": ["C:/path/to/inventor-mcp-server/inventor_mcp_server/server.py"]
    }
  }
}
```
Don't use "cwd" with -m inventor_mcp_server. Claude Code ignores cwd and starts the server from
your project root, where the package can't be found — the process exits immediately and the client only
reports Connection closed. Pointing at the script by absolute path works from any directory.

Configs written for 0.2.x that point at src/server.py still work — that file now forwards to the
inventor_mcp_server package — but please update them; the shim will be removed in a later release.

Alternatively, install it from PyPI — no clone needed, and the config gets a plain command:
```
pip install inventor-mcp-server
```
```
{ "mcpServers": { "inventor": { "command": "inventor-mcp-server" } } }
```
(If your MCP client can't find the command, use the full path printed by where inventor-mcp-server.)
Restart the MCP client (MCP servers load at session start), start Inventor, then ask your AI assistant to build something.

Avoid win32com.client.gencache.EnsureDispatch and CastTo in your own scripts against the same Python install — they generate a gen_py cache that breaks plain GetActiveObject (KeyError: '_dispobj_'). The server itself is immune since 0.5.0 (it never uses gen_py classes), but your scripts aren't: delete %LOCALAPPDATA%\Temp\gen_py if it happens. See the API notes for the full story.

Claude Desktop

Claude Desktop reads the same mcpServers block from claude_desktop_config.json — use the full path
of the Python that has mcp and pywin32 installed (a bare python may be a different one):

{
  "mcpServers": {
    "inventor": {
      "command": "C:/Users/<you>/AppData/Local/Programs/Python/Python312/python.exe",
      "args": ["C:/path/to/inventor-mcp-server/inventor_mcp_server/server.py"]
    }
  }
}

Two things that cost us an afternoon:

Where the file is. The Microsoft Store build of Claude Desktop does not use
%APPDATA%\Claude\claude_desktop_config.json. It keeps its data in
%LOCALAPPDATA%\Claude-Data\claude_<id>\claude_desktop_config.json (the <id> is the package id,
e.g. claude_pzs8sxrjxfjjc). If an edit seems ignored, look in %LOCALAPPDATA%\Claude\Logs\main.log
— its paths show which folder the app really uses.
Edit it only while Claude Desktop is fully closed. The app writes its in-memory copy of the file
back when it quits, so an edit made while it runs is silently thrown away. Quit from the tray icon
(closing the window is not enough), edit, start it again. Settings → Developer should then list
inventor as running; its log is %LOCALAPPDATA%\Claude\Logs\mcp-server-inventor.log.

Several agents, several projects

Claude Desktop starts one server for all its chats, so several agents share it. Each agent gets its
own Inventor:

Tell each agent only its project: "Work in C:\…\Kiosk.ipj." It calls connect(project=…) — the
server reuses the Inventor that already has that project, takes the running one if it is free, or
starts a separate Inventor named after the project.
With several connected, every call carries instance=<name> (the agent learns the name from
connect); a call without it is refused instead of guessing. list_instances shows them all.
Each Inventor has its own call thread, execute_python namespace and manage_call, so one agent's
long job doesn't hold up the others.

Things to know:

Let the server start the Inventors. Open at most one by hand. Windows hands every client the first
Inventor that started, so a second one opened by hand can't be reached (list_instances lists it as
unreachable).
Restarting Claude Desktop (or the server) keeps the Inventors. Every Inventor the server starts is
handed to a small keeper process (keeper.py) that outlives the server; after the restart each agent's
connect(project=…) gets the same Inventor back, open documents and all (connect(pid=…) picks one
explicitly; list_instances shows them). The keeper lets go of an Inventor when its window closes
and exits on its own when it holds none. Inventors opened by hand — and ones started by a server
older than 0.7 — are not kept: save and close those before restarting.
Don't run tests in an agent's Inventor. python tests/smoke_test.py --own starts its own Inventor
and quits it. Exit your own scripts a few seconds after app.Quit(): a process that ends right away
can leave a windowless Inventor.exe behind — which Windows may later hand to the next client that
asks for a new Inventor. Tell an agent's Inventor from such a leftover by its open documents, not by
its start time.

Smoke test

tests/smoke_test.py exercises every geometry-creating code path once against a live
Inventor and reports PASS/FAIL per step — the quickest way to qualify a new Inventor
release or verify your install:

python tests/smoke_test.py            # starts Inventor if needed; closes only the docs it created
python tests/smoke_test.py --keep     # leave the test documents open for inspection
python tests/smoke_test.py --own      # in a separate Inventor it starts and quits — safe while agents work

It also checks every hard-coded enum constant against the live COM type library, so a
renumbered enum in a future release shows up as a named failure instead of a cryptic
COM error. Exit code = number of failed steps.

Current results: 137/137 pass on Inventor 2027.1 (Python 3.12, mcp 1.29 and 2.3).

tests/assembly_smoke_test.py does the same for the assembly tools — it builds a
plate and a pin on disk, places them, and exercises mate / flush / angle / insert
constraints (30/30 pass on Inventor 2027.1).

Skills (optional, recommended)

The skills/ directory contains two Agent Skills that teach Claude the workflow and the Inventor 2026 API quirks:

inventor-modeling — core patterns: units, sketch discipline, hole placement, sheet metal, diagnostic verification, common failure modes
inventor-din-parts — parametric recipes for DIN/ISO standard parts (hex nuts DIN 934 / 439, bolts DIN 933, socket head cap screws DIN 912, countersunk screws DIN 7991, washers DIN 125, flanges DIN 2573) with dimension tables

Install by copying into your skills directory:

cp -r skills/inventor-modeling ~/.claude/skills/
cp -r skills/inventor-din-parts ~/.claude/skills/

Why this exists

Inventor's COM API documentation is wrong or silent about many things in recent versions. This project encodes empirically verified knowledge:

Correct Inventor 2026 enum values (kPartDocumentObject = 12290, dimension orientation 19201/19202/19203, …)
ChamferFeatures.AddUsingDistance(EdgeCollection, d) — the 2026 replacement for the removed CreateChamferDefinition
Sheet-metal FlangeDefinition: the Distance argument is silently ignored; the real height is set via feature.Definition.HeightExtent.Distance.Expression (and the angle is in radians — pass 90 and you get 5156°)
CreateLinearPlacementDefinition requires a BiasPoint argument that dynamic dispatch won't tell you about
Edge indices renumber after every feature; fillets shift adjacent edges
…and more in docs/inventor-api-notes.md

Architecture

inventor_mcp_server/server.py        MCP server (FastMCP / MCPServer) — tool definitions (stdio transport)
inventor_mcp_server/inventor_api.py  InventorConnection — COM wrapper, all geometry logic (mm units)
skills/              Agent Skills for Claude
docs/                Hard-won API knowledge

Contributing

Contributions welcome — see CONTRIBUTING.md for setup, the fast
edit → reload_api loop, and how to add a tool. Especially valuable:

Testing on Inventor 2024/2025 — run tests/smoke_test.py and file an
Inventor version test report (no code needed)
Drawing (IDW) support, and more modeling tools (rib, coil, mirror)
More DIN/ISO part recipes
Bug reports with the exact COM error and Inventor version

Start with a good first issue,
or ask and share what you built in Discussions.

License

MIT — see LICENSE.