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

With no annotations supplied, the description carries the full disclosure burden and says nothing about output format, units (square units?), rounding, or error behavior for an invalid side. It does add one piece of genuine behavioral context — the free-trial-payment model tied to a signed wallet — which is worth some credit but leaves the operational profile largely unexplained.

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 short sentences, front-loaded with the actual function. The trial-call sentence is promotional but brief and does convey pricing context, so it is not wasted.

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 one-formula geometry tool this is nearly sufficient — an agent can infer the operation from the name alone. However, the untyped string parameter and undefined units mean the definition does not fully equip an agent to call it correctly, and there is no output schema to cover the gap.

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% and the single parameter 'side' is typed as a string with no description. The description adds no meaning: whether units are implied, whether decimals or negative values are accepted, and why the type is string rather than number are all unresolved.

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 concrete resource and computed quantity: surface area of a cube. That is unambiguous and matches the tool name, though it does not distinguish itself from nearby siblings such as x402-cube-volume, x402-cube-diagonal, or x402-rect-prism-surface beyond the word 'surface'.

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 guidance on when to use this versus the cube-volume or cube-diagonal siblings, and no mention of preconditions or input expectations. The only extra sentence concerns trial pricing, not usage selection.

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