Get assembly mass properties

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

The readOnlyHint annotation already establishes that this is a safe read operation. The description adds some value by enumerating the returned quantities (mass, volume, centroid, inertia) and the whole-assembly scope, but it does not mention units, coordinate system, or response structure. No contradiction with the annotations.

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 nine words and contains no filler or repetition. The key target ('whole assembly') and the output list are front-loaded, making it easy to scan.

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?

For a read-only query tool with all parameters fully documented in the schema, this description is largely complete: it names the object scope and all returned value categories. It could be more complete by stating units or coordinate frame, and there is no output schema to fall back on, but an agent has enough information to select and invoke the tool correctly.

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 100%, with each required identifier (doc, ws, elem) explained in the context of the Onshape URL. The tool description itself adds no parameter-level meaning, so the schema carries the full burden; the baseline of 3 applies.

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 states what the tool produces—mass, volume, centroid, and inertia—for a whole assembly, and the 'whole assembly' qualifier narrows the scope. However, it does not explicitly contrast this with the closely named sibling onshape_mass_properties, so it is clear but not fully differentiated.

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?

The phrase 'for a whole assembly' implies the intended use case (assembly-level mass properties) and suggests it is not for individual parts. It gives no explicit when-to-use or when-not-to-use guidance and does not name alternatives such as onshape_mass_properties or onshape_measure.

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