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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds the useful methodological detail that the estimate uses the US Navy formula, but it does not disclose the known behavioral quirk that the formula requires a hip measurement for females.

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 sentence is appropriately brief, but 'client and server side from freedailypro' is filler that does not help an agent invoke the tool and crowds out information that would have earned its place.

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 five undocumented parameters, no output schema, and no statement of what the tool returns (percentage, category) or how inputs are measured, the definition leaves significant gaps for an agent to guess at.

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% across five parameters, so the description carries the full burden — and it mentions no parameter at all. It never explains units, the sex enum, or that hipCm is effectively required for female inputs under the Navy formula.

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 resource (body fat) and the method (US Navy style estimate), which separates it from siblings like calculate_bmi and calculate_ideal_weight. However, the 'client and server side from freedailypro' clause is implementation/branding noise that dilutes rather than clarifies purpose.

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 guidance on when to use this tool versus calculate_bmi, calculate_bmr, or calculate_ideal_weight, nor any mention of prerequisites or measurement conditions. Usage is only implied by the tool name.

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