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

Annotations already declare readOnly, idempotent, non-destructive, non-open-world, so the safety profile is covered. The description adds that it returns sunrise/sunset hours and daylight duration, but does not disclose the precision/accuracy of the 'approximate' estimate, which is behaviorally relevant for this tool.

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?

Four short, front-loaded sentences with no filler; purpose comes first, then usage, inputs, outputs, and a cross-reference. Slightly listy but efficient.

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 and 100% param coverage, the description covers purpose, inputs, return values, and a related-bundle pointer. The notable missing piece is a caveat about approximation accuracy and the relationship to calculate_sunrise_sunset.

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% and both parameters (latitude, day_of_year) are documented with ranges in the schema. The description only restates the input names, adding no format or constraint detail beyond the schema, so 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 ('Estimate') and resource (sunrise/sunset times) with the scoping inputs (latitude, day of year). It does not, however, differentiate itself from the sibling calculate_sunrise_sunset, which an agent could plausibly confuse it with given the 'approx' in the 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?

'Use for astronomy or outdoor planning' implies the domain but gives no when-to-use vs when-not guidance and never names calculate_sunrise_sunset as the alternative. Usage is only inferred.

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