URDF

Use this skill for URDF robot-description outputs. Treat URDF work as constrained kinematic modeling, not just XML writing. The main correctness risks are frame placement, joint-axis semantics, unit consistency, mesh scale, inertial data, and generated-artifact drift.

Core Rules

1. Treat the Python source that defines gen_urdf() as the source of truth. Treat configured .urdf files as generated artifacts.
2. Generate only explicit URDF targets. Do not regenerate unrelated CAD, mesh, render, SRDF, SDF, or simulator artifacts from this skill.
3. The scripts/urdf generator validates generated URDFs by default. Do not use or document a separate validate command.
4. Before writing or changing URDF XML, establish the robot's frame, joint, geometry, unit, and assumption ledger. See references/design-ledger.md.
5. Use URDF frame semantics exactly. Joint origins, link frames, joint axes, and visual/collision/inertial origins use different reference frames. See references/frame-semantics.md.
6. Do not infer spatial transforms, mesh units, handedness, axes, or joint signs from vague prose. Use CAD transforms, dimensioned drawings, measured values, existing source data, or explicit documented assumptions.
7. Prefer simple, auditable generator code over clever XML construction. Keep constants named by physical meaning, not by arbitrary numbers.
8. For physical links, model inertial, visual, and collision separately when the target consumer needs them. Frame-only links may intentionally omit mass and geometry.

Workflow

1. Identify the gen_urdf() Python source and target .urdf output.
2. Identify target consumers: RViz, robot_state_publisher, Gazebo/Ignition, MoveIt, a real robot driver, or another simulator.