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

No annotations are supplied, so the description carries the full behavioral burden, and it discloses nothing: no return format, no input expectations, no constraints. A single label is repeated verbatim.

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?

It is short, but only because it is empty; the phrase is a duplicated label rather than a front-loaded, informative statement. Brevity without content does not earn credit.

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 4-parameter tool with no annotations and no output schema, the description provides none of the information an agent would need: no formula, no expected numeric types, no ordering of sides, and no indication of the return value.

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?

Nominally 100% schema coverage, but the schema descriptions are placeholders ('A to process', 'B to process'), so the agent learns nothing about which side each parameter represents or the expected format. The description adds no compensating meaning beyond the parameter letters, so the baseline of 3 is not earned here.

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 is 'Trapezoid Perimeter: Trapezoid Perimeter', which merely restates the tool name with no verb and no scope. It conveys only that some perimeter operation on a trapezoid is involved, matching the 'tautology' criterion rather than stating what the tool actually does.

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 indication of when to use this tool versus the many geometry siblings such as x402-trapezoid-area or x402-regular-polygon-perimeter. No context, prerequisites, or exclusions are provided.

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