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

No annotations and no output schema, so the description carries the full behavioral burden and delivers almost none of it. It does not disclose the formula, whether width/height/length are interchangeable, that the three inputs are string-typed (so numeric strings are expected), unit assumptions, or what the response contains.

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?

A single short sentence with no padding and the key concept front-loaded. The redundant 'Cuboid Diagonal:' prefix echoing the tool name is the only waste, and the brevity reflects under-specification rather than crispness.

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 three-input math helper with no annotations and no output schema, the description is minimally viable but omits what the result is (a scalar diagonal) and how string inputs are handled. Enough to attempt a call, not enough to call confidently.

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%, so the baseline is 3 per the rubric. However, the schema text ('Width to process') is generic boilerplate and the description adds no meaning about ordering, symmetry, or accepted numeric formats, so it neither compensates nor improves on the schema.

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?

Names a specific resource ('space diagonal of a cuboid') and implies the compute action, so the intent is inferable. But it is essentially a restatement of the tool name with a synonym and gives no verb or formula, and it never distinguishes itself from close siblings such as x402-cube-diagonal, x402-cube-space-diagonal, or x402-rectangular-diagonal.

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 when-to-use guidance, no prerequisites, and no mention of alternatives despite many overlapping geometry siblings (cube diagonal, rectangular diagonal, box volume). The agent must guess when this tool is the right pick.

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