bend-elbow

name	bend-elbow
description	Atomic primitive that bends or straightens ONE elbow by rotating the forearm, without moving the shoulder. Use as the elbow building block for curls, waving, reaching to the face, folding the arm, or holding a bent-arm pose. Mentions bend your elbow, bend elbow, flex the forearm, fold the arm, straighten the arm.
category	upper-body
disable-model-invocation	true

bend-elbow

Focused single-DOF slice of the arm chain: elbow flexion only, via the {Side}Forearm joint's Z axis. The shoulder ({Side}UpperArm) is left where it is. For raising/positioning the whole arm see the chain atomic move-arm; for wrist/fingers see move-hand-and-fingers.

Side ∈ Left, Right. Angles ABSOLUTE local euler [x,y,z] deg.

Elbow rule (sign mirrors per side)

• straight elbow: Forearm:[0,0,0]
• bent ~90° (forearm folds up/in): RightForearm:[0,0,90] / LeftForearm:[0,0,-90]
• fully folded (hand toward shoulder): RightForearm:[0,0,140] / LeftForearm:[0,0,-140]

Worked Actions

• "bend your right elbow" → {"durationMs":500,"pose":{"RightForearm":[0,0,90]}}
• "bend both elbows" → {"durationMs":500,"pose":{"LeftForearm":[0,0,-90],"RightForearm":[0,0,90]}}
• "straighten your right arm" → {"durationMs":500,"pose":{"RightForearm":[0,0,0]}}

Limits

Elbows flex one way only — keep magnitude 0..150 and never hyperextend (no opposite sign). Emit only the Forearm joint(s) you change.