mass_propertiesCalculate volume, surface area, centroid, bounding box, and inertia tensor for a 3D object. Input a density to also get mass in kilograms.
Mass properties of a shaped object: volume (mm³), surface area (mm²), centroid, bounding box, inertia tensor. If density (kg/mm³) is given, also returns mass (kg). Steel = 7.9e-6, aluminum = 2.7e-6, ABS = 1.05e-6.
| Name | Required | Description | Default |
|---|---|---|---|
| handle | Yes | ||
| density | No |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate a read-only operation, and the description adds useful behavior: it names the exact output fields, explains the conditional mass calculation when density is provided, and gives concrete typical density values. It does not disclose error behavior or handle requirements, but for a read-only property query the extra context is solid.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is concise and front-loaded with the output list, followed by the conditional mass behavior and useful material density values. Each sentence earns its place; the only minor issue is that the first sentence is a noun phrase rather than an explicit verb-led statement.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description provides a helpful list of return fields and unit annotations. It covers the main thing an agent needs: what the tool returns and how the optional density parameter affects the result. It does not elaborate on handle semantics or error cases, but for a simple read-only calculation tool the description is largely sufficient.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description must compensate. It does explain the density parameter well, including units (kg/mm³) and example values, but it does not explain the required handle parameter at all. Since one of two parameters is meaningfully clarified but the required one is left undocumented, this is only a partial pass.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly identifies the resource ('shaped object') and enumerates the computed properties: volume, surface area, centroid, bounding box, inertia tensor, and optional mass. It does not use a strong main verb like 'calculates' or 'returns' until the second sentence, and it does not explicitly differentiate from sibling tools, so it stops short of a 5.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is given about when to use this tool versus alternatives such as bounding_box, measure_distance, or other analysis tools. The density examples imply a practical use case, but there is no explicit context, prerequisite, or exclusion.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.