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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), so the bar is lower. The description adds genuine output behavior beyond annotations: it reports the formula and the working steps, which matters because there is no output schema. It stops short of describing formatting or unit handling in the result.

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 compact sentences, front-loaded with the resource and supported shapes, then the output behavior. The documentation URL is mildly extraneous but not distracting.

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 no output schema, the description correctly covers what comes back (formula plus working). What it omits is the shape-to-parameter mapping needed to call the tool correctly for non-rectangular shapes, and why 'z' exists and when it is required.

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 80%, so the schema already documents x (Length), y (Width), unit, and shape; baseline is 3. The description adds nothing about which of x/y/z applies to which shape, which is the key ambiguity here (e.g., a circle needs only one dimension, but x/y/z are all free-form numbers with 'z' completely undocumented in both schema and description).

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?

States a specific resource (area) and enumerates the exact shapes supported, which lets an agent know it covers rectangle/square/triangle/circle/trapezoid/parallelogram/ellipse. It does not, however, distinguish itself from overlapping siblings like circle_calculator, triangle_calculator, or square_footage_calculator.

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 or when-not-to-use guidance. Given the dense sibling set, the definition should have said whether this is the general-purpose geometry area tool that supersedes the shape-specific siblings; instead the agent must guess.

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