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

Annotations already declare readOnlyHint, idempotentHint, and a closed-world profile, so the safety burden is light. The description adds genuinely useful context beyond that: the named Boer formula, that both lean AND fat mass are returned, and that output is expressible in kg or pounds. It omits that all seven inputs are optional and defaulted, but that lives in the schema.

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 plus a reference URL; the concrete example is front-loaded and the operational instruction follows immediately. The trailing webpage link adds little for an agent and is the only filler.

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 seven parameters, the description does a fair job by showing a sample result magnitude, but it never explains how the metric and imperial parameter families interact (which fields to populate under which 'units' value). Adequate, but not fully sufficient for a 7-param tool with a dual-unit input design.

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 schema already documents every parameter, making 3 the baseline. The description only loosely implies the unit dimension ('in kg or pounds') and never clarifies the metric/imperial parameter split (cm/ft/inch, kg/lb) that the schema exposes.

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 names a specific verb+resource (estimate lean and fat mass) and even anchors it with a worked example (70 kg, 175 cm, Boer formula), so the purpose is unambiguous. It does not, however, differentiate itself from close siblings like body_fat_calculator, bmi_calculator, or ideal_weight_calculator, which an agent must choose among.

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?

'Enter your height, weight and sex' implies the input conditions, but there is no explicit when-to-use guidance and no exclusion relative to the many body-composition siblings. Usage is inferable but the agent gets no routing help.

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