Skip to main content
Glama
Lecoeurdelest

mujoco-mcp

by Lecoeurdelest
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python

mujoco_set_running

Idempotent

Pause or resume a visible MuJoCo simulation session at real-time speed, optionally updating actuator controls during playback.

Instructions

Play/pause the visible session at approximately real-time speed.

Open a viewer first. Optional ctrl changes persist; this can update controls
during playback. Pause before deterministic mujoco_step calls. Closing the
window or resetting pauses playback. Instability pauses automatically and
appears in runtime_error; call mujoco_reset to recover.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
ctrlNoActuator controls: full vector in actuator order, or {actuator_name: value} for a subset. Persists on the session until changed.
runningYes
session_idYes

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4.5/5.0
Behavior5/5

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

Beyond the annotations (readOnlyHint false, idempotentHint true), the description discloses that ctrl changes persist, playback can be updated live, closing the window or resetting pauses playback, and instability auto-pauses with recovery via mujoco_reset. No contradiction with annotations; it adds substantial behavioral detail.

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 a compact paragraph with a front-loaded purpose, followed by tightly packed behavioral notes. Every sentence adds unique, non-redundant information without fluff, making it efficient and easy to scan.

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 complexity (play/pause with live ctrl updates and error recovery), the description covers prerequisites, timing, side effects, and recovery. It even references the output mechanism (runtime_error) and pairs with an output schema, so return details are not needed here. No critical usage context is missing.

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 only 33% (only ctrl has a description). The description does not explicitly explain running or session_id, though running is implied by 'play/pause' and session_id is a standard identifier. It adds value for ctrl by noting persistence, but fails to fully compensate for the low schema coverage on the other two parameters.

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 clearly states 'Play/pause the visible session at approximately real-time speed,' specifying the action and resource. It distinguishes itself from siblings like mujoco_step (single-step) and mujoco_reset (recovery) by focusing on the play/pause control of the viewer session.

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

Usage Guidelines4/5

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

Provides a prerequisite ('Open a viewer first') and a key usage condition ('Pause before deterministic mujoco_step calls'), and explicitly routes to mujoco_reset for recovery from instability. It doesn't explicitly enumerate all alternative tools, but the context given is actionable and sufficient for common scenarios.

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

Deploy Server

Other Tools