Bimwright

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Bimwright — the predictable Revit MCP server.

Pure C#. Apache-2.0. 28 tools across Revit 2022–2027, transaction-safe and auditable. Extensible via ToolBaker when you need more.

Built for AI agents and BIM workflows that want reversible, reviewable edits — every change shows up in the undo stack.

Key traits:

• Full R22–R27 span. One codebase, six plugin shells, .NET 4.8 → .NET 10. Most peers skip at least one year.
• Pure C# + Apache-2.0. No Node.js runtime beside Revit. Enterprise-safe license + audit-ready dependency graph.
• Transaction-safe batching. batch_execute wraps a command list in one Revit TransactionGroup — one undo, atomic rollback on failure.
• Progressive disclosure. --toolsets + --read-only gate what the model sees. Weak models stay sharp.
• ToolBaker self-extension. The model writes, compiles, and registers new Revit tools at runtime (Debug).

Architecture

MCP client (Claude Code, etc.) ⇄ stdio ⇄ Bimwright.Rvt.Server (.NET 8) ⇄ TCP/Pipe ⇄ Bimwright.Rvt.Plugin.R<nn> (inside Revit.exe) ⇄ Revit API

Two processes. The server is a .NET global tool; the plugin is a per-Revit-year add-in DLL. See ARCHITECTURE.md for the full picture.

Install

1. Server — .NET tool

dotnet tool install -g Bimwright.Rvt.Server
bimwright-rvt --help

Requires .NET 8 SDK on the machine that runs the MCP client.

2. Plugin — Revit add-in

Download the latest release from GitHub Releases. Extract it and run:

pwsh install.ps1            # detects every installed Revit year
pwsh install.ps1 -WhatIf    # preview without changes
pwsh install.ps1 -Uninstall # clean removal

The script detects installed Revit versions via HKLM:\SOFTWARE\Autodesk\Revit\ and copies the matching plugin into %APPDATA%\Autodesk\Revit\Addins\<year>\Bimwright\.

3. Wire up your MCP client

Add one entry per Revit year to your client's MCP config (e.g. .mcp.json):

{
  "mcpServers": {
    "bimwright-rvt-r23": {
      "command": "bimwright-rvt",
      "args": ["--target", "R23"]
    }
  }
}

Drop the --target flag and Bimwright auto-detects the running Revit instance via discovery files in %LOCALAPPDATA%\Bimwright\.

Supported MCP clients

Broader client-compat matrix is on the v0.2 roadmap.

Quickstart — 5 minutes to first tool call

1. dotnet tool install -g Bimwright.Rvt.Server + pwsh install.ps1.
2. Open Revit, click the Bimwright → Start MCP ribbon button.
3. In your MCP client, run tools/list — you should see the default toolsets (query, create, view, meta).
4. Call get_current_view_info — you'll get back a DTO like:

   { "viewName": "Level 1", "viewType": "FloorPlan", "levelName": "Level 1", "scale": 100 }
   

5. Try something real:

   batch_execute({
     "commands": "[
       {\"command\":\"create_grid\",\"params\":{\"name\":\"A\",\"start\":[0,0],\"end\":[20000,0]}},
       {\"command\":\"create_level\",\"params\":{\"name\":\"L2\",\"elevation\":3000}}
     ]"
   })
   

   One undo step, both ops committed atomically.

Toolsets

28 tools across 10 groups. Four groups are on by default (query, create, view, meta); the rest opt in via --toolsets or config.

Enable with --toolsets query,create,modify,meta or --toolsets all. Add --read-only to strip create/modify/delete regardless of what you requested.

Supported Revit versions

Compile gate is 6/6; runtime verified 4/4 on R23–R26 (see A1 in the commit history). R22 and R27 ship on compile-evidence because the stack is identical to R23 and R26 respectively.

Security

• Default loopback bind. TCP transport listens on 127.0.0.1 only. Opt in to 0.0.0.0 with BIMWRIGHT_ALLOW_LAN_BIND=1.
• Token-gated handshake. Every connection must present a per-session token written only to %LOCALAPPDATA%\Bimwright\portR<nn>.txt.
• Strict schema validation. Malformed tool calls are rejected with an error-as-teacher envelope (error, suggestion, hint) before any handler runs.
• Path-leak mask. Handler exceptions are sanitized before they reach the MCP response or logs — no absolute paths, UNC shares, or user-home dirs leak out.

See the security appendix for the full threat model.

Configuration

Three layers, later wins: JSON file → env vars → CLI args.

JSON file path: %LOCALAPPDATA%\Bimwright\bimwright.config.json.

ToolBaker — Cook your own tool with your true dataflow

Generic MCP tools force one-size-fits-all workflows. Real BIM tasks aren't — when the model stitches 10+ primitive tools together to do your actual job, you pay in time and tokens every single session. That was the itch. ToolBaker is the scratch.

You describe the workflow once. The model writes C# against the Revit API, bake_tool compiles it through Roslyn into an isolated AssemblyLoadContext, and registers it as a first-class MCP tool. Next session, your workflow is a single call — no re-planning, no re-invented glue code, no token burn.

How it works:

1. Describe your real dataflow in plain language (e.g. "schedule every door by fire rating, tag failures, export to CSV").
2. The model generates a handler matching the IRevitCommand contract.
3. bake_tool compiles via Roslyn, links against the live Revit API, loads into a sandboxed assembly context.
4. SQLite persists the bake. Auto-registered on every future Bimwright session.
5. Call it like any built-in — same schema validation, same transaction safety.

Gated behind --enable-toolbaker (off by default). send_code_to_revit — the unsandboxed escape hatch — is Debug-build only.

Documentation

• ARCHITECTURE.md — process model, transport, multi-version strategy, ToolBaker pipeline.
• CONTRIBUTING.md — dev setup, build matrix, coding style.
• docs/roadmap.md — v0.2 (MCP Resources, ToolBaker hardening), v0.3 (async job polling, aggregator listings), v1.0 (governance).

License

Apache-2.0. See LICENSE.