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EL4CTEO

Roblox Studio MCP

Solid modelling

geometry
Destructive

Perform constructive solid geometry on Roblox parts: union, subtract, intersect, and fragment to build complex shapes without importing meshes.

Instructions

Cuts, joins and shatters parts with real constructive solid geometry.

This is how to build a shape that is not a box without importing a mesh: subtract a door out of a wall, union several parts into one solid, intersect to keep only the overlap, fragment to shatter something into debris.

subtract and intersect need the parts to actually overlap, and they fail differently when they do not. intersect returns nothing, which comes back as an error rather than a silent no-op. subtract returns the subject UNCHANGED — a full-size copy of it, reported as a created part — because cutting nothing out of something legitimately leaves it whole. So a subtract that succeeds is not proof that anything was cut: check the positions overlap with inspect first, or compare the result's size against the original.

Results keep the original's material, colour and anchoring. Roblox returns bare grey MeshParts, so a brick wall with a hole cut in it would otherwise come back as a grey slab — correct geometry that looks like a mistake.

The originals are consumed unless keepOriginals is set. The whole operation is one undo step.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
opYes'union' merges, 'subtract' cuts `with` out of `path`, 'intersect' keeps only the overlap, 'fragment' shatters `path` into pieces.
nameNoName for the result. Defaults to the original's.
pathYesThe part being operated on — the one cut from, for subtract.
withNoThe other parts. Required for union, subtract and intersect.
parentNoWhere to put the result. Defaults to the original's parent.
piecesNofragment only: roughly how many pieces to break into.
studioIdNoTarget Studio; omit for the active one.
splitApartNoReturn disconnected chunks as separate parts rather than one.
keepOriginalsNoLeave the input parts in place instead of consuming them.
collisionFidelityNoHow exactly the result collides. Precise is expensive — raise it only for a surface players walk on.Default
Behavior5/5

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

The description goes far beyond the annotations by disclosing key behavioral details: originals are consumed unless `keepOriginals` is set, the whole operation is one undo step, `subtract` returns the subject unchanged when there is no overlap, `intersect` returns an error on no overlap, and results inherit material/color/anchoring. It even warns about Roblox returning grey MeshParts. This is excellent behavioral disclosure for a destructive tool.

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 long but every sentence earns its place. It front-loads the core purpose, then moves through operation examples, failure modes, material preservation, and consumption semantics in a logical order. The caveats about subtract and intersect are high-value and would otherwise be discovered only at runtime.

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 destructive, multi-operation tool with 10 parameters and no output schema, the description covers all critical runtime behaviors: operation semantics, overlap requirements, failure modes, material inheritance, input consumption, undo behavior, and performance trade-offs. The remaining parameter details are already fully documented in the schema, so nothing essential is missing.

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?

Schema coverage is 100%, so the baseline is 3. The description adds meaningful semantic context beyond the schema: it explains the failure modes of `subtract` and `intersect`, clarifies that `keepOriginals` affects consumption of inputs, and notes that results retain material/color/anchoring. This helps the agent reason about parameter effects without reading the schema alone.

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 opens with a specific verb and resource: 'Cuts, joins and shatters parts with real constructive solid geometry.' It then enumerates the four operations and gives concrete examples (subtract a door out of a wall, union parts, etc.), which clearly distinguishes this from sibling tools like create, modify, or delete.

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?

The description explains when this tool is the right choice: 'This is how to build a shape that is not a box without importing a mesh.' It also directs the agent to use `inspect` to verify overlap before subtracting, which is a practical alternative. It does not explicitly list all the sibling tools it should not be used instead of, but the use case is clearly scoped.

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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