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Roblox MCP

Roblox MCP

by sdhzcxnb0
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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set_property

Sets a single property on a Roblox instance using plain JSON scalars or literals like Vector3, Color3, Enum, or CFrame, with changes recorded for undo.

Instructions

Set one property on an instance. Values accept plain JSON scalars or literals such as 'Vector3(4,1,2)', 'Color3(1,0,0)', 'Enum.Material.Neon', 'CFrame(0,5,0)'.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "path": "<path>",
      "property": "<property>",
      "value": "<value>"
    },
    "name": "set_property"
  }
}

Input Schema

NameRequiredDescriptionDefault
pathYes
valueYes
propertyYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.2/5.0
Behavior3/5

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

No annotations are supplied, so the description carries the full burden. It does disclose non-obvious behavior worth crediting: only a single property is set per call and values are coerced from string literals like 'Vector3(4,1,2)' or 'Enum.Material.Neon'. It omits reversibility/undo, whether writes persist to the saved place, and error behavior for invalid paths or type-mismatched values.

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?

Two tight sentences with the core action front-loaded and the value-format detail second, which is the right order. No filler, though the value examples could be trimmed slightly without loss.

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

Completeness3/5

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

For a simple three-parameter mutation tool with no annotations and no output schema, the description covers the action and the trickiest parameter but not the addressing scheme or the result of a failed/invalid call. An agent would still have to guess how to construct 'path'.

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 0% and all three parameters are bare titles, so the description must compensate. It substantially clarifies 'value' by naming accepted scalar and literal forms, but leaves 'path' (instance addressing format) and 'property' (naming/casing rules) entirely unexplained.

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

Purpose4/5

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

States a specific verb and resource ('Set one property on an instance'), which is clear and distinct from the read-oriented siblings like get_instance and get_tree. It doesn't explicitly contrast itself with create_instance, delete_instance, or execute_luau, which are the mutation alternatives.

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

Usage Guidelines2/5

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

There is no explicit when-to-use guidance, no mention of when to prefer execute_luau for batch or computed changes, and no prerequisites such as whether the target must exist or be loaded in the open place. The only implied usage comes from the verb itself.

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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