Diagnoses 3D PhysX collision and trigger problems. Use when OnCollisionEnter or OnTriggerEnter doesn't fire, objects pass through each other, raycasts miss, or a MeshCollider misbehaves. Also answers 2D and DOTS physics best-effort if no dedicated skill is available.
Install
npx skills add Unity-Technologies/unity-agent-plugin --skill physics-3d-collisionnpx skills add Unity-Technologies/unity-agent-plugin --skill physics-3d-collision -a claude-code -gnpx skills add Unity-Technologies/unity-agent-plugin --skill physics-3d-collision -a codex -ggemini skills install https://github.com/Unity-Technologies/unity-agent-plugin.git --path skills/physics-3d-collisiongh skill install Unity-Technologies/unity-agent-plugin physics-3d-collisiongit clone --depth 1 https://github.com/Unity-Technologies/unity-agent-plugin /tmp/Unity-Technologies__unity-agent-plugin
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/Unity-Technologies__unity-agent-plugin/skills/physics-3d-collision ~/.claude/skills/physics-3d-collision # Claude Code
cp -R /tmp/Unity-Technologies__unity-agent-plugin/skills/physics-3d-collision ~/.agents/skills/physics-3d-collision # Codex, Cursor, Gemini CLI, Copilot, OpenCode