Free tools for labeling furniture 3D models include Blender (with built-in annotation/text tools), SketchUp Free (via native text or simple plugins), and MeshLab (for metadata/visual labels).
Blender lets you add editable text or interactive annotations directly to models; SketchUp Free is ideal for basic name or dimension labels; MeshLab helps tag material or product details.
If you’re new to 3D labeling, start with SketchUp Free for its easy interface, or Blender if you need flexibility for complex annotations.