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2021 Roblox Studio MCP Bridge

2021 Roblox Studio MCP Bridge

by aswdffdas-sudo
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
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run_playtest

Starts a Roblox playtest, monitors runtime errors for a set duration, captures a screenshot, and stops the test automatically.

Instructions

Runs an autonomous test: starts playtest, monitors for runtime errors over duration, captures screenshot, and stops test

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "run_playtest"
  }
}

Input Schema

NameRequiredDescriptionDefault
modeNoTest mode: 'play' (Play Solo) or 'run' (Run)play
durationNoSeconds to run test (2 to 30, default 5)
capture_screenNoWhether to snap a screenshot during the test

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv1.5.6

TDQS

A3.5/5.0
Behavior3/5

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

With no annotations, the description carries the full burden. It usefully discloses the sequence and side effects (starts, monitors runtime errors, snapshots, stops), but omits whether the call blocks for `duration`, what happens if errors occur, and how the captured errors/screenshot are surfaced to the agent.

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?

A single front-loaded sentence that names the operation and then enumerates its steps in order with zero filler.

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?

There are no annotations and no output schema, so the description is the only place return semantics can live, yet it does not say how runtime errors or the screenshot are reported back. For a stateful, multi-step mutation tool this leaves a meaningful gap.

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 mode, duration, and capture_screen are each already documented in the schema with defaults, ranges, and enum meanings. Baseline 3 applies; the description adds no parameter detail beyond what the schema carries.

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 ('Runs an autonomous test') and enumerates the lifecycle it performs: start, monitor, screenshot, stop. It is clear what the tool does, but it never explicitly distinguishes itself from the siblings start_playtest and stop_playtest, which it internally composes.

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

Usage Guidelines3/5

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

The word 'autonomous' implies a hands-off, one-shot workflow versus manually driving start_playtest/stop_playtest, but no when-to-use or when-not-to-use condition is stated and no alternative is named.

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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