Research-Stack/5-Applications/text-to-cad/skills/urdf/references/generator-contract.md

URDF Generator Contract

Use this reference when creating or editing Python sources that generate URDF files.

Source Of Truth

The Python source that defines gen_urdf() is source of truth. The configured .urdf file is generated and should not be hand-edited.

Envelope Contract

gen_urdf() must be a top-level zero-argument function returning an envelope with:

• xml: complete URDF XML as a string
• urdf_output: relative path to the generated .urdf file

The urdf_output path:

• is relative to the owning Python source
• must use POSIX / separators
• must end in .urdf
• is resolved as a file path, not through a harness root

The host project may impose its own layout policy, but the URDF skill runtime does not hardcode a project directory.

Runtime Behavior

5-Applications/scripts/gen_urdf runs only gen_urdf(). It does not regenerate STEP, STL, GLB/topology, DXF, or CAD render artifacts.

If URDF mesh references depend on updated CAD outputs, regenerate those CAD targets separately with the CAD skill.