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. The description adds only that it returns a next reapply time, which the output schema already carries; no auth, rate-limit, or edge-case behavior is disclosed.

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?

Front-loaded with the core action and short overall, but the 'Inputs' line redundantly restates schema fields while containing an inaccurate entry, so not every sentence 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 an output schema present, return values need not be explained, and annotations carry the safety profile; the three real parameters are schema-documented. The remaining gap is the inaccurate 'activity'/'water exposure' input reference, which slightly undercuts completeness.

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%, so the schema fully documents the three real parameters (spf, skin_type, uv_index). However, the description's 'Inputs' list introduces 'activity (sweat/swim)' and 'water exposure,' neither of which exists in the schema, adding a phantom parameter that could mislead an agent. This detracts rather than adds meaning.

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: 'Compute when to reapply sunscreen' with the basis (SPF, activity, water exposure). Against a sibling list of hundreds of calculate_* tools, this is unambiguous and instantly distinguishable.

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?

'Use for sun safety' is an implied-domain hint rather than explicit when-to-use guidance. The 'See list_bundles' pointer is a related-tool reference, not a selection criterion against alternatives, so the agent gets context but no exclusions or conditions.

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