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 fully covered structurally. The description adds the deterministic formula name and the return key, which is modest additional context but nothing about accuracy limits or edge cases (e.g. output near BMI extremes).

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 short sentences, front-loaded with the core action and method, with no padding. The explicit 'Returns: {body_fat_pct}' is slightly redundant given an output schema exists, and the list_bundles pointer is tangential, but the text is otherwise tight.

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, deterministic three-input calculator with a full schema, complete annotations and an output schema, the description supplies everything needed to invoke it correctly: inputs, method and the returned field. Only edge-case behavior and the sibling-vs-sibling choice are left unstated.

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% and each of the three parameters carries its own description, range and enum, so the schema does the heavy lifting. The description only echoes the parameter names as inputs without adding format or constraint detail beyond the schema; 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+resource ('Estimate body fat percentage') and names the exact inputs (BMI, age, sex) and method (Deurenberg equation), which implicitly separates it from the sibling calculate_body_fat_navy. It never names that sibling explicitly, so the differentiation is inferential rather than stated.

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?

Usage is only implied: an agent can infer it should be called when BMI, age and sex are available. There is no guidance on when to prefer this over calculate_body_fat_navy or calculate_bmi, and the closing pointer to list_bundles is a cross-reference, not a when-to-use rule.

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