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by CarlxsMG
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set_physics_constraint_drives

DestructiveIdempotent

Set linear/angular drives, breakable thresholds, projection, and collision on a physics constraint actor component to define joint behavior for simulation.

Instructions

Set linear/angular drives (motors), breakable thresholds, projection, and collision/dominance on a world APhysicsConstraintActor's UPhysicsConstraintComponent — the "behavior beyond limits" (read-modify-write; only provided fields change; idempotent set-to-fixed-value). Authoring-only: the values are written into the component's serialized ConstraintInstance template and persist; the live motor torque is only applied while simulating (PIE). Distinct from the UPhysicsAsset constraint drives (set_physics_asset_constraint_drives), which author a ragdoll joint inside an asset.

Returns: { constraint_actor_name: string, constraint_component: string, applied_count: int, angular_drive_mode: string, angular_orientation_drive: bool, angular_velocity_drive: bool, angular_drive_spring: number, angular_drive_damping: number, angular_drive_force_limit: number, angular_orientation_target: [number], linear_position_drive: bool, linear_velocity_drive: bool, linear_drive_spring: number, linear_drive_damping: number, linear_drive_force_limit: number, linear_position_target: [number], linear_breakable: bool, linear_break_threshold: number, angular_breakable: bool, angular_break_threshold: number, projection_enabled: bool, projection_linear_alpha: number, projection_angular_alpha: number, projection_linear_tolerance: number, projection_angular_tolerance: number, parent_dominates: bool, disable_collision: bool, constraint_broken: bool, note: string, updated: bool }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
break_constraintNoOptional: if true, immediately break the (live) constraint via BreakConstraint().
linear_breakableNoOptional: the joint can break under linear force.
parent_dominatesNoOptional: the parent body is unaffected by the child's motion.
angular_breakableNoOptional: the joint can break under angular force.
disable_collisionNoOptional: disable collision between the two constrained bodies.
angular_drive_modeNoOptional angular drive mode: SLERP|TwistAndSwing (dispatches the orientation/velocity enable path).
projection_enabledNoOptional: enable projection (post-solve position/angle fixup).
linear_drive_springNoOptional linear drive spring/stiffness.
angular_drive_springNoOptional angular drive spring/stiffness.
linear_drive_dampingNoOptional linear drive damping.
angular_drive_dampingNoOptional angular drive damping.
constraint_actor_nameYesLabel/name of the APhysicsConstraintActor (as spawned by spawn_physics_constraint).
linear_position_driveNoOptional: enable the linear position drive (applied to all 3 axes).
linear_velocity_driveNoOptional: enable the linear velocity drive (all 3 axes).
angular_velocity_driveNoOptional: enable the angular velocity drive.
linear_break_thresholdNoOptional linear break force threshold.
linear_position_targetNoOptional [x, y, z] target position.
angular_break_thresholdNoOptional angular break torque threshold.
projection_linear_alphaNoOptional semi-physical linear projection alpha [0..1].
linear_drive_force_limitNoOptional linear drive force limit (0 = unlimited).
projection_angular_alphaNoOptional semi-physical angular projection alpha [0..1].
angular_drive_force_limitNoOptional angular drive force/torque limit (0 = unlimited).
angular_orientation_driveNoOptional: enable the angular orientation (position) drive.
angular_orientation_targetNoOptional [pitch, yaw, roll] target orientation in degrees.
projection_linear_toleranceNoOptional projection linear tolerance.
projection_angular_toleranceNoOptional projection angular tolerance in degrees.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.1.0

TDQS

A4.4/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: clarifies that only provided fields change, that it is idempotent set-to-fixed-value, that it is authoring-only and persists into the serialized ConstraintInstance template, and that live motor torque applies only under PIE simulation. This meaningfully contextualizes the destructiveHint=true annotation (break_constraint breaks the live constraint).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The behavioral sentences are front-loaded and dense with no filler. The trailing Returns enumeration is long, but since there is no output schema it is functionally load-bearing rather than padding, so it stays efficient overall.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 26-parameter mutation tool with no output schema, the description covers target, scope, mutation semantics, persistence, sibling differentiation, and the return shape. Nothing an agent needs to invoke it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so per-parameter meaning is already fully documented in the schema. The description groups the parameter families (drives, breakable, projection, collision/dominance) but adds no syntax or format detail beyond what the schema states, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Set) plus the exact resources: linear/angular drives (motors), breakable thresholds, projection, and collision/dominance, on a named target (APhysicsConstraintActor's UPhysicsConstraintComponent). It explicitly distinguishes itself from the sibling set_physics_asset_constraint_drives (world constraint vs asset-embedded ragdoll joint).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It names an alternative (set_physics_asset_constraint_drives) and the condition that selects each (world actor vs physics asset). It also frames the operation with read-modify-write and idempotent semantics, giving useful context. However, it does not address the nearby sibling set_constraint_limits, so the alternative routing is not fully exhaustive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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