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IBM

Physics MCP Server

by IBM

calculate_moment_of_inertia

Compute rotational inertia for objects like spheres, rods, disks, and boxes based on mass distribution and rotation axis to analyze rotational motion.

Instructions

Calculate moment of inertia for various shapes.

Moment of inertia (I) is the rotational equivalent of mass. It determines
how difficult it is to change an object's rotation. Depends on both mass
distribution and rotation axis.

Args:
    shape: Shape type - "sphere", "solid_sphere", "hollow_sphere", "rod", "disk", "cylinder", "box"
    mass: Mass in kilograms
    radius: Radius for sphere/disk/cylinder (meters)
    length: Length for rod (meters)
    width: Width for box (meters)
    height: Height for box/cylinder (meters)
    depth: Depth for box (meters)
    axis: Rotation axis - "center", "end" (for rod), "x", "y", "z" (for box)

Returns:
    Dict containing:
        - moment_of_inertia: I in kg⋅m²
        - shape: Shape type
        - axis: Rotation axis

Common formulas:
    - Solid sphere (center): I = (2/5)mr²
    - Hollow sphere (center): I = (2/3)mr²
    - Rod (center): I = (1/12)mL²
    - Rod (end): I = (1/3)mL²
    - Disk (center): I = (1/2)mr²

Example - Spinning wheel:
    result = await calculate_moment_of_inertia(
        shape="disk",
        mass=5.0,  # 5kg wheel
        radius=0.3  # 30cm radius
    )
    # I = 0.225 kg⋅m²

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
shapeYes
massYes
radiusNo
lengthNo
widthNo
heightNo
depthNo
axisNocenter
Behavior4/5

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

With no annotations provided, the description carries full burden and does well by explaining the tool's purpose, providing formulas, and showing an example calculation. It doesn't mention error handling, precision, or computational limits, but gives substantial behavioral context through the detailed example and formula references.

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?

Well-structured with clear sections (purpose, args, returns, formulas, example). The physics explanation could be slightly condensed, but every sentence adds value. The example is detailed but helpful for understanding usage.

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?

For a calculation tool with 8 parameters, 0% schema coverage, and no output schema, the description provides exceptional completeness. It explains all parameters, provides return format details, includes common formulas for reference, and gives a working example - covering everything needed to use the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage and 8 parameters, the description fully compensates by explaining every parameter's meaning, units, and valid values. It clearly maps shape types to required dimensions (radius for spheres/disks, length for rods, etc.) and explains axis options with context for each shape.

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 the tool calculates moment of inertia for various shapes, specifying the exact physical quantity and providing context about its meaning. It distinguishes itself from sibling tools by focusing specifically on rotational inertia calculations rather than other physics calculations like forces, energies, or simulations.

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 description implies usage through the example and parameter explanations, showing this is for calculating rotational inertia of specific shapes. However, it doesn't explicitly state when to use this tool versus alternatives like calculate_torque or calculate_angular_acceleration, nor does it mention prerequisites or exclusions.

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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