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EL4CTEO

Roblox Studio MCP

Collision groups

collision

Control collisions between specific part groups in Roblox Studio. Create groups, assign parts, and set collidable to allow pass-through without affecting other collisions.

Instructions

Controls which parts physically collide with which.

This is the right answer to 'these should pass through each other'. The alternative — turning CanCollide off — disables collision against everything, so a ghost that should pass through walls also falls through the floor.

The order is: create a group, assign parts to it, then set what it is collidable with. A group with nothing assigned does nothing.

Assigning a Model assigns every part inside it, which is almost always what is meant.

Groups are not undoable and not scoped to a session: remove when one was created to try something and is no longer wanted, rather than leaving it registered in the place indefinitely. The built-in "Default" group cannot be removed.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
withNocollidable only: the other group.
groupNoThe group's name. Required for everything but list.
pathsNoassign only: parts or models to put in the group.
actionNo'list' shows existing groups and changes nothing. 'remove' unregisters a group entirely — not the same as un-assigning parts from it.list
studioIdNoTarget Studio; omit for the active one.
collidableNocollidable only: whether the two groups collide. False makes them pass through.
Behavior5/5

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

Beyond the annotations (readOnlyHint: false, etc.), the description discloses important behavioral traits: groups are not undoable, not scoped to a session, and removing unregisters a group entirely. It also explains that assigning a Model assigns all its parts and that a group with no assignments does nothing, adding significant transparency.

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

Conciseness5/5

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

The description is well-structured: it starts with the core purpose, then covers the primary use case and alternative, followed by operational order and caveats. Each sentence adds value with no fluff, making it efficient and easy to follow. Despite being slightly long, it remains concise due to the density of useful information.

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?

Given the absence of an output schema, the description provides enough contextual information for an agent to use the tool correctly. It explains behavior, side effects, constraints (Default group cannot be removed), and the exact sequence of actions. No critical aspect is left unexplained, making it complete for practical use.

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

Parameters4/5

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

The schema descriptions already cover all parameters (100% coverage), so the baseline is 3. The description adds meaningful context by explaining the action flow (create, assign, collidable) and clarifying that 'remove' is not the same as un-assigning parts, which helps interpret the 'action' parameter. This goes beyond the schema but not maximally, so a 4 is appropriate.

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?

The description clearly states the tool's purpose with a specific verb ('Controls') and resource ('which parts physically collide with which'), immediately distinguishing it from sibling tools like geometry or script_edit. It also provides a concrete use-case ('these should pass through each other') and contrasts with the CanCollide alternative, making the purpose unmistakable.

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

Usage Guidelines5/5

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

It explicitly states when to use this tool over the alternative (CanCollide) by explaining the downside of the alternative (ghost falls through floor). It also gives a step-by-step order of operations (create, assign, collidable) and clarifies when to use 'remove' versus un-assigning, leaving no ambiguity about usage scenarios.

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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