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

Annotations already declare read-only, idempotent, closed-world, so safety is covered; the description adds genuinely new behavioral context: results are in local clock time to the minute, day-length deltas vs the previous day are included, and three twilight bands plus golden/blue hours are reported. Gaps: no mention of behavior at polar latitudes where sunrise/sunset may not occur.

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?

One dense sentence front-loads the primary outputs and appends secondary ones, with zero filler. Slightly list-heavy, but every clause maps to a real capability the agent would want to know about.

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?

An output schema exists, so return values needn't be explained, yet the description's enumeration of outputs usefully signals what the tool can be selected for. Combined with 100% schema coverage and clear annotations, the definition is sufficient to call correctly; only polar-edge behavior is unaddressed.

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 parameters are already fully documented and the baseline is 3. The description reinforces the defaults (today, local clock time) but adds no syntax or constraint meaning beyond what the schema and enum already state.

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?

Names a specific resource (sunrise, sunset, solar noon, day length) plus the secondary outputs (twilight phases, golden/blue hours) and the scoping ('at a place on a day, today by default'). An agent immediately knows this is the solar-timing tool, distinct from moon_times or solstice which cover different bodies/events.

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 implied by the phrase 'at a place on a day (today by default)', which hints at the common no-args case, but there is no explicit when-to-use vs sun_calendar (a sibling covering many days) or guidance on choosing city vs lat/lon/tz. The agent must infer the alternative selection from the schema.

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