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

Annotations already declare this as read-only, idempotent, non-destructive and closed-world. The description adds useful behavioral context beyond that: it filters to naked-eye-visible passes and limits results to the next 10 days, though it does not discuss permissions, rate limits, or ordering.

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 definition is a single front-loaded sentence with no filler, and the key visibility and timeframe constraints appear early. It is slightly dense because it also lists return fields that the output schema likely covers.

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 forecast tool with rich schema coverage, annotations and an output schema, this description supplies the essential scope, visibility filter, and time horizon. The remaining omissions are mostly explicit sibling routing and default-language behavior, which are handled elsewhere or are minor.

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 lat/lon/city/lang parameters are already well documented, including the nearest-voivodeship-seat fallback. The description confirms the Polish-city scope but adds no parameter syntax or format details beyond the schema.

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 states the resource and scope: visible ISS passes over a Polish city during the next 10 days, including per-pass start, peak, end and brightness. It is specific enough to be distinguishable, but it does not explicitly contrast itself with sibling tools such as tonight_sky or planets_tonight.

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 visibility and 10-day forecast framing, so an agent can infer this is for ISS pass lookups rather than aurora, meteor shower, or planet queries. However, there is no explicit when-to-use versus alternatives guidance or any exclusion criteria.

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