export_cad | Reference

export_cad evaluates an IR document through the WASM kernel and writes the result to a file on disk. The output format is determined by the filename extension.

Input Schema

irDocumentrequired

IR document from create_cad_document or create_cad_loon. Can be provided in JSON or compact format -- the tool parses both.

filenamestringrequired

Output filename with extension. The extension determines the export format. Supported extensions: .stl, .glb.

Supported Formats

STL (.stl)

Binary STL format, the standard for 3D printing. The tool tessellates the BRep geometry into a triangle mesh and writes a single combined mesh for all scene parts. Binary STL is used exclusively (no ASCII STL option) because binary is smaller and faster, and all modern slicers support it.

STL files do not contain material, color, or unit information. By convention, vcad exports in millimeters.

{
  "ir": "# vcad 0.2\nC 50 30 5\nROOT 0 default",
  "filename": "bracket.stl"
}

GLB (.glb)

glTF Binary format for 3D visualization. GLB preserves per-part PBR materials (color, metallic, roughness), making it suitable for rendering in web viewers, game engines, and AR/VR applications. Each scene root becomes a separate mesh with its assigned material.

{
  "ir": "# vcad 0.2\nM aluminum 0.9 0.9 0.92 0.95 0.3\nC 50 30 5\nROOT 0 aluminum",
  "filename": "bracket.glb"
}

Return Value

On success, the tool returns a JSON text response with export metadata:

{
  "path": "/Users/you/project/bracket.stl",
  "bytes": 42684,
  "format": "stl",
  "parts": 1
}

Field	Type	Description
`path`	string	Absolute path to the written file
`bytes`	number	File size in bytes
`format`	string	Export format (matches the extension)
`parts`	number	Number of parts exported

The file is written to the current working directory of the MCP server process. Use absolute paths in the filename to write to a specific location.

Error Handling

The tool throws an error in these cases:

No parts to export. The document evaluates to zero parts, typically because the roots array is empty or all roots reference missing nodes.

Unsupported format. The filename extension is not .stl or .glb. The error message lists the supported extensions.

Evaluation failure. The kernel fails to evaluate the IR document, usually due to invalid boolean operations (e.g., non-overlapping operands for intersection) or missing node references.

I/O failure. The output path is not writable (permissions, disk full, etc.).

{
  "content": [{"type": "text", "text": "Error: Unsupported format: .obj. Use .stl or .glb"}],
  "isError": true
}

Workflow

The recommended MCP workflow is:

create_cad_document or create_cad_loon to build geometry
inspect_cad to verify dimensions and volume
export_cad to write the final file

The inspect step catches geometry problems (unexpected volume, wrong bounding box) before they reach the export, saving time on iteration.

STEP export

For STEP format export, use the export_step tool from the STEP I/O toolset instead of export_cad. STEP preserves the exact BRep representation rather than tessellating to triangles.

File location

The MCP server writes files relative to its current working directory, which is typically the directory where npx @vcad/mcp was launched. To control the output location, use an absolute path in the filename parameter.