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

With no annotations, the description bears the full burden of behavioral disclosure, and it reveals nothing beyond the computation's label. There is no mention of the formula, no explanation of how a cube's side length is supplied given the empty input schema, and no statement of return format or edge cases — an agent cannot tell how to invoke it correctly.

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 five words long — this is under-specification rather than disciplined conciseness. There is no substantive content to be concise about; the text only echoes the title.

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 empty schema, no annotations, and no output schema, the description is the only guidance an agent has, and it resolves nothing: how to pass input, what result to expect, and when to choose this over x402-cube-diagonal are all unanswerd. This is effectively unusable as a standalone definition.

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?

The schema has zero properties, so per the rubric a 0-param tool earns baseline 4; there is nothing for the description to document. However, the description does not clarify the awkward fact that computing a cube's space diagonal implies a side length that the schema never captures, which leaves the calling convention ambiguous.

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 'Space diagonal of a cube' restates the tool name nearly verbatim and adds no new information — it is effectively a tautology. It does not state the formula, what input it needs, or how it differs from siblen x402-cube-diagonal, x402-cuboid-diagonal, or x402-rectangular-diagonal. An agent choosing between these siblings gets zero disambiguating signal from this text.

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 alternative tools named, and no exclusion conditions are given. The siblen list contains x402-cube-diagonal which is indistinguishable from this tool based on the description, yet there is no hint about which one to pick for a given request.

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