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

With no annotations provided, the description carries the full burden of behavioral disclosure. It goes well beyond a typical calculator description by noting that BMI is a screening tool, not a diagnosis, does not distinguish muscle from fat, and can misclassify athletic people—instructing the agent to caveat when relevant.

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?

The description is well-structured and front-loaded: core purpose first, then outputs, usage guidance, unit conversion, and caveats. Every sentence earns its place, and the only overlap with the schema is the Args block, which still adds value through units and examples.

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?

Since there is no output schema, the description appropriately details return values (BMI value, category classification, healthy weight range) and the exact category names. Combined with conversion constants and the clinical caveat, an agent has everything needed to invoke the tool and interpret its result correctly.

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%, but the Args section fully compensates by adding units and concrete examples: weight in kilograms (e.g., 75 for 75kg) and height in metres (e.g., 1.75 for 175cm). This removes all ambiguity about parameter meaning and units.

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 opens with a specific verb and resource: 'Calculate Body Mass Index (BMI) from metric measurements.' It then names the exact outputs (BMI value, category classification, healthy weight range), making the tool's purpose unmistakable and clearly distinct from the sibling calculators.

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?

It explicitly states 'Use for any BMI question' and provides realistic example prompts like 'what is my BMI' and 'am I a healthy weight.' It also anticipates the main alternative input scenario by explaining exactly how to convert imperial units to metric, so an agent knows when and how to invoke the tool.

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