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Roblox Executor MCP Server

by okenjioxx
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TypeScript
Local

Record EVERY property that changes on an Instance over a window (event-driven)

watch-property-changes
Read-onlyIdempotent

Connects an Instance's Changed signal for a set duration to record every property that changes, revealing which properties a Roblox action mutates.

Instructions

Connects an Instance's Changed signal for a bounded window and records EVERY property that changes (its name plus the new value), then disconnects and returns the log. This is the discovery counterpart to watch-instance-property (inspection), which polls a SINGLE named property you already know: use watch-property-changes when you DON'T know which property to watch and want to see everything that moves — e.g. perform an action in-game and learn which of an Instance's properties the game actually mutates, or catch a property you didn't expect to change. It uses a signal CONNECTION (Instance.Changed), not a function hook, so it is low-risk; the connection is always disconnected at the end of the window. HOW IT WORKS: resolves the Instance, connects inst.Changed (which fires with the changed property NAME for plain Instances), and for each fire pcall-reads inst[prop] and appends { property, newValue, t }; then task.wait(s) for the duration and disconnects. The call BLOCKS for roughly durationMs while listening — perform the triggering action (click/move/etc.) shortly before or during the watch. NOTE: on some objects the Changed signal carries a Property-value-changed payload rather than a name (e.g. ValueBase objects fire with the value); this tool records the raw signal argument as the property identifier in that case. Returns { Path, ClassName, durationMs, changeCount, changes = [{ property, newValue, t }], truncated } or { error }. Signature: { instancePath: string, durationMs: any?, limit: any?, threadContext: number? }. Phase: observe; cost=medium; idempotency=read-only. Requires: active-client, resolved-target. Produces: bounded-event-snapshot. Safety: read-only. On failure: inspect tool-schema for exact fields, defaults, constraints, and an invocation example.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNoMaximum number of change records to keep (default 500, max 2000). When more changes fire than this cap, the extra ones are dropped and `truncated` is set true.
durationMsNoHow long to listen, in milliseconds (default 4000, min 100, max 30000). The tool BLOCKS for about this long; trigger the change you want to observe shortly before or during this window.
instancePathYesLuau expression resolving to the Instance to watch, e.g. 'game.Players.LocalPlayer.Character.Humanoid', 'game.Workspace.Part', or 'game.Players.LocalPlayer.PlayerGui.HUD.Frame'. Evaluated as `return <instancePath>` and must resolve to an Instance.
threadContextNoOptional Roblox thread identity for this call; omit it to use the server default.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv2.0.0-spies.2

TDQS

A4.6/5.0
Behavior5/5

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

Annotations already cover readOnly/idempotent/non-destructive, but the description adds substantial behavior beyond them: signal CONNECTION vs function hook, guaranteed disconnect at window end, blocking for ~durationMs, the ValueBase payload edge case, and the truncation cap.

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?

Front-loaded with purpose and the sibling contrast, and every major section is useful. Some redundancy exists (read-only stated in annotations, idempotency line, and Safety line; the signature duplicates the schema), which keeps it from a 5.

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?

With no output schema, the description fully documents the return shape ({ Path, ClassName, durationMs, changeCount, changes[], truncated } or { error }), plus prerequisites and failure handling, leaving nothing essential missing for a 4-param read tool.

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 the schema already documents all four parameters. The description mostly restates them (blocking for durationMs, signature line), adding little syntax or meaning beyond what the schema provides, so baseline 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 (connects/records/disconnects) and resource (an Instance's Changed signal over a bounded window), and explicitly distinguishes itself from the sibling watch-instance-property by naming the counterpart and contrasting discovery vs inspection.

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?

Gives an explicit when-to-use rule ('when you DON'T know which property to watch'), names the alternative (watch-instance-property) and the condition that selects it, and adds operational guidance about triggering the action during the blocking window.

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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