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EL4CTEO

Roblox Studio MCP

Performance and memory

performance
Read-onlyIdempotent

Detect performance issues by reading engine counters, profiling script CPU usage, and analyzing scene memory and unparented instances.

Instructions

Reads the engine's own counters, and can run the script profiler.

snapshot returns what the Developer Console shows: frame, physics and render times in milliseconds, instance and part counts, draw calls, network rates, and memory broken down by category. Use it to answer 'why is this place heavy' with numbers instead of guesses.

profile runs Studio's script profiler — the Script Performance window — for seconds and reports which scripts consumed CPU. It blocks for that long, so keep it short. It only sees code that actually runs, so start a playtest first; profiling an idle edit session returns nothing.

coverage reports which lines of which scripts actually executed — dead code, untested branches, whether a fix was even reached. Pass enable first, then play, then read the coverage back FROM THE PLAYTEST session, not the editor: instrumenting is per data model, and the playtest is a different one. enable is remembered for the place and re-applied by each new session as it loads. Pass an empty enable array to stop.

What it can and cannot see: instrumentation is fixed when a script is first compiled, so it measures modules required after that point — where most game logic lives — but never a script that starts with the place, which the data model compiles before any plugin exists. Those report 0 lines and are named as unmeasurable rather than counted as dead code.

scene breaks the place down by what it is actually made of: instances by category, triangles and draw calls, and the assets holding script, animation and audio memory — each named, so "2.4GB of memory" becomes "this animation is 138KB and these are the Animators using it". It also reports UNPARENTED INSTANCES, which is the closest thing here to a leak detector: objects still alive with nothing holding them in the tree, invisible to find and to tree because they are in neither.

Frame and network figures are only meaningful while something is running. Instance counts and memory are useful in edit mode too.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
opNo'snapshot' reads counters now; 'profile' samples running scripts; 'coverage' reports which lines have executed; 'scene' breaks the place down by what it is made of.snapshot
enableNocoverage only: scripts to start measuring. Remembered for this place and switched on by every session that loads afterwards, so a playtest instruments them before its scripts run. An empty array stops instrumenting.
secondsNoprofile only: how long to sample. The call blocks for this long.
sectionNoscene only: return just one section instead of all six.
studioIdNoTarget Studio; omit for the active one.
frequencyNoprofile only: samples per second. Higher is more precise and costlier.
includePluginsNoprofile only: include Studio plugins in the results. Off by default — an idle Studio is mostly plugin activity, which buries the place's own scripts.
Behavior1/5

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

The description is highly transparent about behavior, including blocking profile calls, per-data-model instrumentation, and the fact that unparented instances are not in the tree. However, it explicitly documents that coverage's `enable` is 'remembered for the place and re-applied by each new session as it loads', which is a persistent side effect, while annotations declare `readOnlyHint: true`. This is an annotation contradiction, so per the rubric this dimension must score 1.

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 earns every sentence: each paragraph maps to one operation, uses code spans for parameter values, and front-loads the core purpose before diving into caveats. It is dense, well-structured, and contains no filler.

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?

Given the tool's multi-operation complexity and lack of an output schema, the description is remarkably complete. It covers what each operation returns, prerequisites, timing constraints, state persistence, and limitations. Remaining details like `studioId`, `frequency`, and `includePlugins` are adequately covered by the input 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 already 100%, so the baseline is 3. The description adds meaningful behavior beyond the schema: it explains the profile workflow, the coverage lifecycle from enable through playtest session to stop, and the practical caveat that profiling an idle edit session returns nothing. This is enough to push the score above baseline.

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 opening sentence states a specific activity — reading engine counters and running the script profiler — and the description then cleanly differentiates the four operations: snapshot, profile, coverage, and scene. It also distinguishes itself from sibling tools like find and tree by noting that unparented instances are invisible to both, making its unique resource clear.

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?

The description gives explicit when-to-use guidance for each mode: snapshot to answer 'why is this place heavy', profile after starting a playtest, coverage with the enable-then-play-then-read flow, and scene for composition and memory breakdowns. It also states exclusions — idle profiling returns nothing, and scripts compiled before the plugin exists are unmeasurable.

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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