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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral context beyond that: computation is performed locally from NOAA equations, no third-party API is called, results default to UTC, and polar day/night conditions are specially reported. This clearly conveys what the agent can expect behaviorally.

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 compact and well-structured: it opens with the core function, then adds computation details, time zone behavior, edge cases, and example use cases. Every sentence contributes useful information without padding or repetition.

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?

For a read-only, idempotent calculation tool with fully documented parameters, the description is nearly complete. It explains output time zone convention, polar cases, and typical applications. The only gap is that it does not detail the exact output schema/fields returned, but since there is no output schema, a bit more precision on return shape would have made it fully complete.

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 four parameters. The description adds a helpful tz_offset example and clarifies UTC default, but it does not meaningfully expand on the schema's parameter definitions. Baseline 3 is appropriate given the schema's completeness.

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 clearly identifies the operation ('Compute sunrise, sunset, solar noon, and civil twilight') and the resource (a latitude/longitude and date). It is specific and distinct from sibling tools like weather forecasts or tide predictions, making the tool's purpose unambiguous.

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?

The description gives concrete use cases ('daylight planning, photography golden-hour timing, or agriculture and energy calculations'), which implies when to call it. However, it does not explicitly name alternative tools or state when not to use this one, so the guidance remains implicit rather than comparative.

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