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

No annotations are provided, so the description carries the whole burden. It usefully discloses scope limits ('Informational only, not medical advice') and the calculation basis via the schema's 280-day back-calculation. However, it never says what happens when neither optional input is supplied or when both lmp and dueDate are given, which is a real ambiguity for a tool with zero required parameters.

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 sentences, front-loaded with the computation and its outputs, followed by the scope disclaimer. No filler, and the disclaimer earns its place in a medical-adjacent context.

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 and no annotations, the description does the important work of naming what is returned (weeks/days, trimester, progress). The remaining gap is input-selection behavior when zero or two date inputs are supplied, which matters given that all three parameters are optional.

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 100%, so the baseline is 3, but the description adds something the schema does not: that LMP and due date are alternative entry points rather than complementary inputs. It still does not resolve precedence when both are supplied, so it does not reach 5.

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 ('work out') and a precisely enumerated result set: weeks and days pregnant, the trimester, and progress through the 40 weeks. The 'from either the LMP or the due date' clause implicitly distinguishes it from sibling calculate_due_date, which runs the conversion the other way.

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?

The description says it can be driven from LMP or due date, which is mild usage guidance, but never states when to pick this tool over calculate_due_date, calculate_ovulation, or the other siblings. There is no explicit alternative routing or when-not-to-use condition.

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