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

With no annotations, the description carries the full burden and does disclose important behavior: what the tool returns, the synthesisPossible=false edge case when the sun never gets high enough, and what atTime adds. It does not explicitly state that the tool is read-only or side-effect-free, though that is strongly implied by the get-style output description.

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 front-loaded with purpose and uses three efficient sentences with no filler. The first sentence is dense and carries several concepts at once, but every sentence earns its place by covering purpose, edge-case behavior, and sibling routing.

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?

Given ten parameters, no annotations, and no output schema, the description gives enough completeness: it explains the core return semantics, the false edge case, and the usage boundary against the year-scale sibling. The input schema already covers parameter defaults and constraints at 100%.

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%, so the schema already documents all ten parameters thoroughly. The description reinforces atTime and target IU but largely duplicates schema semantics rather than adding new meaning, so the baseline 3 is appropriate.

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 states a precise verb-and-resource purpose: the solar vitamin D synthesis window for one specific day at a location for a personal profile. It enumerates the key outputs (UV threshold, best hour, clear-sky minutes, atTime-specific minutes) and distinguishes this single-day tool from the year-scale sibling by name.

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 gives explicit when-to-use guidance: single-day questions only. It also names the alternative (get_vitamin_d_year) and the exact condition that should route the agent there, including the anti-pattern of calling this once per date.

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