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EL4CTEO

Roblox Studio MCP

Drive the player during a playtest

character

Automate playtest character movement and actions for gameplay testing, including pathfinding, jump, sit, equip/activate tools, and state checks to verify results.

Instructions

Moves and acts as the player character in a running playtest, so gameplay can be tested without asking the user to play it.

moveTo walks to a position or to an instance, following a path computed around walls and gaps rather than a straight line into them. It reports whether it ACTUALLY ARRIVED and how far short it stopped — a route blocked by something you did not know about otherwise looks identical to a successful walk.

act does the one-shot things worth testing: jump, sit, stand, respawn, kill (to exercise the death and respawn path), teleport, and equip/activate to use a Tool — which is how combat gets tested, since Activate is exactly what a mouse click triggers. Note that teleport skips everything in between, so triggers and collisions along the route do not fire — walk if you are testing those.

state reports position, health, walk speed and what the humanoid is doing. Call it before and after anything else here.

This drives the Humanoid directly rather than simulating keystrokes, which is the right tool for going places: pathfinding around a wall is one call here and a sequence of guessed key presses otherwise. For anything bound to a control rather than to movement — does E open the door, does the sprint key work, does Escape close the menu — use input, which sends real key and mouse events.

REQUIRES A RUNNING PLAYTEST, and the character lives in the playtest's data model — address these to the playtest's studioId from list_studios, not the editor's. Run mode has no character at all; use playtest op=play.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
opYes'moveTo' walks somewhere, 'act' performs an action, 'state' only reports.
toNoTarget position, e.g. "25, 5, -10". Used by moveTo and by teleport.
pathNomoveTo only: walk to this instance instead of a coordinate.
toolNoequip only: the Tool's name.
actionNoact only: what to do. 'equip' takes a Tool from the Backpack or StarterPack, 'activate' uses it (what a mouse click triggers).
directNomoveTo only: walk straight at the target without pathfinding. Use when a route is reported unreachable but you want to see what happens.
playerNoWhich player, by name. Omit for the only one; needed in a multiplayer test.
canJumpNomoveTo only: allow the path to include jumps.
studioIdNoThe PLAYTEST session's id — not the editor's. See list_studios.
Behavior5/5

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

Beyond the annotations, the description discloses key behavioral traits: moveTo reports whether it actually arrived and how far short it stopped, teleport skips triggers and collisions, state reports position/health/walk speed/activity, and the tool drives the Humanoid directly rather than simulating keystrokes. This is substantial, operationally important context that the annotations alone do not provide.

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?

The description is well-structured with clear sections for moveTo, act, and state, plus a use-case comparison and a requirement note. It is long, but justified given the tool's complexity and nine parameters; it avoids repetition and front-loads the core purpose.

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?

This is nearly a complete operational guide: it gives prerequisites, alternative-tool routing, per-operation behavior, caveats around teleport, parameter relationships, and even suggests calling state before and after actions. It is sufficient for an agent to know when and how to invoke the tool, including the playtest-instance context that could otherwise be a common failure.

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 100%, but the description adds real semantic value: it clarifies the purpose of moveTo vs act vs state, documents that equip takes a Tool from Backpack/StarterPack, notes activate corresponds to a mouse click, and explains which operations use the path parameter. It doesn't enumerate every single parameter (e.g., direct and canJump are only lightly touched on), but the extra context meaningfully improves understandability.

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 description begins with a specific verb and resource: 'Moves and acts as the player character in a running playtest,' and breaks out the three operations moveTo, act, and state. This makes the tool's scope unmistakable and distinguishes it from sibling tools like input, which is explicitly described as sending real key and mouse events.

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 provides unusually explicit usage guidance: it tells agents to use this tool for movement/character actions, to use input for control-bound interactions, and to use playtest op=play when there is no running playtest. It even explains what to do when a route is unreachable via the direct parameter, as well as to address calls to the playtest studioId from list_studios, not the editor's.

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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