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. The one piece of genuine added context is naming the Naegele rule, which tells the agent the computation basis, but nothing is said about the output form or how referenceDate alters 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?

A single front-loaded fragment with zero padding. It is terse to the point of being a label rather than a sentence, but nothing in it is 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 two-parameter tool with no output schema and no schema descriptions, the description leaves the agent guessing at input format (ISO date? string?), the role of referenceDate, and whether the result is a date or a gestational age. The annotations carry safety only, not semantics.

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 description coverage is 0%, so the description is the only place parameter meaning could come from, and it supplies none: neither the required lastMenstrualPeriod nor the optional referenceDate is explained, and no date format is given. The mention of 'Naegele rule' only weakly implies that a last menstrual period is the anchor input.

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?

Names a specific calculation (pregnancy due date) with the underlying method (Naegele rule), which is enough to distinguish it from the many other calculate_* siblings. It falls short of 5 because it never explicitly contrasts itself with neighbours like calculate_age, relying on the topic noun to do the separating.

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 statement of when to use this versus other calculators, no prerequisites, and no guidance on what the caller must supply. An agent must infer everything from the tool name and schema.

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