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2021 Roblox Studio MCP Bridge

start_playtest

Launches a Roblox Studio playtest in Play Solo (F5) or Run/Server Simulation (F8) mode to test gameplay or server physics.

Instructions

Starts a playtest in Roblox Studio (F5 for Play Solo, F8 for Run / Server Simulation)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
modeNo'play' for Play Solo (F5), 'run' for physics/server simulation (F8)play

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv1.5.6

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden. It does not state whether the call blocks, what side effects occur in Studio, what permissions are needed, or what happens on success/failure. The F5/F8 detail is already in the schema, so it adds little behavioral context.

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?

A single sentence with no wasted words and the core action front-loaded. The parenthetical is arguably redundant with the schema, but it does not bloat the description.

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

Completeness2/5

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

For a mutation/action tool with no annotations and no output schema, the description is too thin. It omits what the tool returns, whether it blocks, and any prerequisites such as needing an active Studio connection, all of which an agent may need. The simple schema helps, but the description should do more.

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 coverage is 100%, so the baseline is 3. The description repeats the mode-to-shortcut mapping but does not add syntax, default behavior, or format details beyond what the schema already provides.

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 ('Starts a playtest in Roblox Studio'), so the action is immediately clear. However, it does not differentiate from the sibling tool 'run_playtest', leaving ambiguity about which one to choose.

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?

No when-to-use guidance, no alternatives named, and no prerequisites stated. The parenthetical maps modes to keyboard shortcuts but does not say when to use this tool versus run_playtest or stop_playtest.

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