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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered and the description's job is lighter. It adds real context beyond that: the exact outputs returned (gallons, litres, cubic feet, cubic metres, surface area, formula) and the shape/depth input modes it accepts. It does not discuss error behavior or what happens with mismatched shape/dimension combos, keeping it off a 5.

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 dense, front-loaded paragraph that begins with the trigger condition and ends with the sibling routing rule; every clause carries information. It is list-heavy (shape names, unit names, wall heights) and slightly overpacked for a single sentence, but there is no filler to remove.

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 an output schema present, return values needn't be spelled out, yet the description still names them, and it covers the input-mode space (all shapes, three depth configurations, ft/m). The one omission is that freeform shapes require a supplied area — visible only in the schema — so the description is nearly, but not entirely, self-sufficient.

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 83%, so the schema already documents most parameters and a baseline 3 would be acceptable. The description adds value by tying the shape enum to the depth configurations available (single depth, shallow + deep end, or above-ground 48/52/54 in wall height) and by stating that dimensions may be in feet or metres, which clarifies parameter interactions rather than restating individual fields.

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 states a precise verb and resource — compute gallons/litres/cubic feet a pool holds from shape and size — and enumerates the supported shape, depth and unit variants. An agent can distinguish it immediately from chemical_dose, pump_size and heater_size, which are sizing/chemistry tools rather than geometry calculators.

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?

It opens with an explicit trigger ('Use this when someone wants to know how many gallons...') and then names the three sibling tools plus the selecting condition: 'use it before chemical_dose, pump_size or heater_size when only dimensions are known.' That is a clear when-to-use rule with an explicit alternative.

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