mass

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

With no annotations, the description carries full burden and does add value: it discloses units (kg), the computation source ('uses Fusion's physical-properties calc'), and material provenance ('whatever the body has been assigned'). However, it never explicitly confirms this is a read-only, side-effect-free query, and the null-body_name behavior is only implied.

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?

Two front-loaded sentences with no wasted words. The first sentence delivers the core purpose and scope; the second adds behavioral detail on material and computation. Appropriately sized for a simple query tool.

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 only one parameter, no annotations, and no output schema, the description explains the return values (mass in kg, material name, density, volume), the scope, and the computation source — covering the essentials for a simple getter. Minor gap: no explicit handling of the null body_name case, though 'all bodies' implies it.

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 coverage is 0%, so the description must compensate. It implicitly maps body_name to the scope ('for a body or all bodies'), suggesting null targets all bodies. This adds meaning beyond the schema, but the mapping is implied rather than explicit (e.g., 'if body_name is null, returns all bodies' is never stated).

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 uses a clear resource ('mass (kg), material name, density, and volume') with explicit scoping ('for a body or all bodies'). It distinguishes from sibling tools like volume and center_of_mass by bundling material/density with mass, though 'Return' is a generic verb and the overlap with the volume sibling is not fully clarified.

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 on when to use this tool versus alternatives. The scope ('for a body or all bodies') gives context on invocation, but there is no mention of when to prefer this over sibling query tools like measure, volume, or center_of_mass, and no when-not-to-use exclusions.

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