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name: robot-model-import description: "Load, inspect, validate, and troubleshoot IKPy robot models from URDF, MJCF, or IKPy JSON metadata." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Robot model import

Use this sub-skill when a robot description must become an IKPy Chain, when an imported chain has the wrong path or joint count, or when a URDF/MJCF parser error needs diagnosis. Start with the smallest model inspection that answers which links, joints, bodies, and path names are present.

• For loader signatures, path semantics, element-to-URDFLink mapping, and orientation conventions, read api-reference.md.
• For self-contained URDF/MJCF examples and smoke fixtures, read workflows.md. The bundled scripts/make_tiny_models.py creates temporary examples without repository assets.
• For actionable parser and data failures, read troubleshooting.md.
• python scripts/inspect_model.py --help provides a no-write model inspection command. It reports source names and chain shape, and can optionally run FK.

The central distinction is structural: URDF has root-level link and joint records traversed as an alternating path, while MJCF nests body records and follows child bodies. IKPy represents each URDF/MJCF joint (or a fixed body/explicit tip offset) as a URDFLink; the source URDF link records are not chain links. Keep explicit False values in an active_links_mask for the origin and fixed tip entries; do not rely on the constructor's last-entry warning to repair a NumPy boolean mask. Pass a full joint vector, including inactive entries.

Use Chain.from_urdf_file or Chain.from_json_file for URDF-backed models and Chain.from_mjcf_file for MJCF. Use ikpy.urdf.utils.get_urdf_tree only for optional structural inspection, and keep rendering concerns in visualization-geometry. Route FK/IK method selection to chain-kinematics and JAX execution to jax-backend.