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

Annotations already declare the full safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's remaining burden is light. It adds the shape of the result, but says nothing about it being a non-medical estimate, assumptions behind 'safe' exposure, or behavior at extreme UV values. Adequate but thin.

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 purpose sentence is front-loaded and clean, but the explicit return-field enumeration duplicates the output schema and the trailing list_bundles pointer is tangential for a single-purpose calculator. Neither is harmful, but neither earns 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 a full output schema, complete parameter documentation, and annotations covering the safety profile, the definition gives an agent everything needed to invoke it correctly. Only a brief caveat about the advisory nature of the exposure estimate is missing.

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% — both uv_index and the six-value skin_type enum are fully documented in the schema, including the Fitzpatrick meaning. The description merely restates the parameter names, adding no syntax, units, or edge-case meaning 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 and resource ('Calculate safe sun exposure time') and names the two inputs that drive it (UV index, Fitzpatrick skin type), so the agent knows exactly what it produces. It does not, however, distinguish itself from adjacent siblings such as calculate_sunscreen_reapply or calculate_garden_sunlight_hours.

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 when-to-use, when-not-to-use, or alternative-tool guidance. The closing pointer to list_bundles is a navigation aid for related calculators, not a condition that helps the agent choose this tool over a sibling.

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