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

Annotations already declare readOnly/idempotent/closed-world, so safety is covered. The description adds genuine value with no output schema present by naming what is returned (ACE category, fat mass, lean mass) and the formula used, but it omits that hips are only relevant for females in this formula and says nothing about metric/imperial switching.

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?

Front-loaded single sentence delivering formula, inputs and outputs, plus a web page link. Efficient overall, though the trailing URL is promotional rather than functional.

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 13-parameter tool with no required fields and no output schema, the description covers inputs and outputs but leaves real ambiguity unresolved: which units param to use, that height/weight and circumference each have metric and imperial duplicates, and that hip measurements apply only to women.

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 100%, so the schema already documents all 13 parameters with units and ranges; the description only restates neck/waist/hips. Baseline 3 is appropriate since the schema does the heavy lifting and the description adds no syntax or unit-selection guidance.

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 ('Body fat % from a tape measure'), names the exact formula (US Navy Hodgdon–Beckett), lists the inputs (neck, waist, hips) and outputs (ACE category, fat mass, lean mass). This clearly distinguishes it from siblings like bmi_calculator, lean_body_mass_calculator and waist_to_hip_ratio_calculator.

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 tool is implicitly scoped to a tape-measure method, which hints at when it applies, but there is no explicit when-to-use/when-not guidance and no reference to the alternative body-composition siblings an agent would have to choose between.

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