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

Annotations already declare readOnly, idempotent, and non-destructive, so safety is covered. The description adds a credit cost ('cost: 1 credit'), which is genuinely useful context an agent cannot get from structured fields, though nothing is said about output units or rounding.

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: purpose plus formula first, then cost in parentheses. Nothing is redundant and the most decision-relevant information leads.

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 simple three-parameter stateless calculator with a self-evident output and a fully documented schema, the description covers purpose, units, and cost. The only minor gap is not stating the output unit (kg/m²) or precision, which is low-risk here.

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% and the schema already documents each parameter with units and defaults. The description restates the metric/imperial unit pairing but adds no format, range, or validation detail beyond what the schema provides, so the baseline 3 applies.

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 ('Calculates Body Mass Index (BMI)') and includes the exact formula, which unambiguously distinguishes it from the many other calculate_* siblings such as calculate_area or calculate_calorie_intake.

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 unit systems and required inputs imply when the tool applies, but there is no explicit when-to-use or when-not-to-use guidance, and no pointer to alternatives such as convert_units for callers who only need unit conversion.

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