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

Annotations already establish this as a safe, idempotent, closed-world read. The description adds genuinely non-obvious context: values are computed from the lunar cycle rather than observed, and they are explicitly a 'planning estimate, not a sighting report' — a reliability caveat an agent could not infer from structured fields.

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?

Two sentences, both load-bearing: the first establishes resource, place, and computation basis; the second delivers the reliability caveat. Nothing is padded and the scope is front-loaded.

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 one-parameter, no-output-schema read tool this covers what is needed to call it correctly and interpret results. The only mild gap is that it does not say what a returned record contains or how far ahead windows are projected, though the 'upcoming' framing largely covers that.

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?

The single parameter has 100% schema description coverage, so the schema carries the meaning of 'limit'. The description says nothing about it, which is the expected baseline when the schema is complete, but it adds no extra semantics.

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 names a specific resource (box jellyfish watch windows), pins down the geography (Hawaii's south-facing shores such as Waikiki and Ala Moana), and states the derivation rule (days 8-12 after each full moon). The scope is narrow enough that no sibling ambiguity remains even though the other tools cover unrelated domains.

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 frames the tool as a planning aid rather than a live sighting feed, which implicitly tells the agent when the output is appropriate. However, there is no explicit when-to-use statement, no mention of what to reach for when the user wants actual sightings or alerts, and no prerequisites.

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