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

No annotations are supplied, so the description carries the full disclosure burden and delivers almost nothing: no units, no formula, no note on whether both radii are required (required=0 in the schema is potentially misleading), and no statement of the return value. It is silent rather than wrong, so 2 rather than 1.

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?

One short sentence, front-loaded, with no filler or repetition. It is efficient, though its brevity borders on under-specification rather than earning credit as a 5.

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 trivial two-input geometry calculation this is roughly adequate: the purpose and parameters are covered by name plus schema. However, with no output schema and no annotations, the description leaves the return value and unit conventions unspecified.

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 two documented parameters, so the baseline is 3. The description does not name or clarify majorRadius/minorRadius, and does not resolve the string-typed radii or the zero-required anomaly, so it adds no value beyond 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?

The description names a specific verb+resource ('Surface area' of a 'torus'), so an agent can tell it computes a geometry quantity. It does not differentiate itself from the close sibling x402-torus-volume beyond the resource noun, but the distinction is still inferable from the name/description pair.

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?

There is no statement of when to use this tool versus alternatives such as x402-torus-volume or the other surface tools (sphere-surface, cylinder-surface). No prerequisites, no input expectations, no exclusions are given.

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