Use this when the user has a photo, PDF drawing, STEP, STL, DXF, SVG or 3MF file on their device and you need it in a kernelCAD tool (trace_from_image, drawing_to_cad, mesh_to_features, inspect of:"step", or lib.fromSTEP / fromSTL / fromDXF / fromSVG / referenceImage in a script). Do not ask the user to paste the file as text or base64, and do not type coordinates from an image by hand. Returns a one-time uploadUrl (valid 30 minutes) and an asset reference. Give the user the link; after they say the upload is done, pass the asset value ("asset:") as the file argument, for example trace_from_image({ imageUrl: "asset:" }) or lib.fromSTEP("asset:"). If the file is already at a public https:// URL, pass that URL instead. On clients that support MCP URL elicitation the upload page opens for the user directly and the call returns once the file is stored (status "uploaded"); then use the asset right away without asking the user anything.