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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is fully covered. The description adds essentially nothing behavioral beyond stating output units, which the output schema already provides. It is a pure computation, so a baseline 3 is appropriate.

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?

Five short, front-loaded sentences with the core purpose and units stated first; little waste. The input and cross-reference sentences are compact, though the invented shape/radius detail is wasted (and misleading) text.

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?

An output schema exists so return values need not be explained, and the description covers purpose and units. But it misrepresents the input surface (nonexistent shape/radius params, missing substrate_cm), so an agent lacks a reliable picture of what to pass.

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?

With 0% schema coverage the description must compensate, and it partially does by naming L×W×H in cm. But it invents inputs that do not exist ('shape (rectangular/cylindrical/bow-front)', 'radius×height') and omits the real substrate_cm parameter, actively misdescribing 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?

States a specific verb and resource ('Compute aquarium water volume') plus output units (L and US gallons), which clearly distinguishes it from generic siblings like calculate_volume or calculate_pool_volume. Clear and specific, though it doesn't explicitly name the sibling it is not.

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?

'Use for fishkeeping, dosing, and stocking decisions' gives concrete usage context, and it cross-references list_bundles for related calculators. However, it offers no when-not guidance or direct alternative (e.g., calculate_volume for non-aquarium shapes).

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