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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuine behavioral context — the 3-day lookahead limit and the rule that visibility requires a sunlit satellite against a dark sky — but says nothing about response volume (how many passes typically return) or how min_elevation filters both culminations and visibility.

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?

Everything is packed into a single front-loaded sentence that leads with the operation and follows with required inputs and output content; no filler. It is dense to the point of being slightly hard to scan, which is why it is not a 5.

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 9-parameter tool with no output schema, the description does the important work of describing what comes back and the visibility semantics. Defaults for days, start, lang and min_elevation are only in the schema, but that is an acceptable division of labor.

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 89%, so the baseline is 3. The description does add real value for `id` by giving NORAD examples (ISS=25544, Tiangong=48274, Hubble=20580) and restates the east-positive longitude convention, but it leaves days, start, lang, height_m and min_elevation entirely to 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 names a specific verb and resource — computing satellite passes over a place — and enumerates the returned quantities (rise, culmination, set, azimuth/compass, elevation, naked-eye visibility). It is unmistakable what the tool does, but it never names an overlapping sibling such as perigee_sky or perigee_tonight to disambiguate.

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 states the operating context clearly: supply latitude/longitude in degrees (east positive) and an IANA time zone for local times, with a horizon of up to 3 days. There is no explicit when-not-to-use guidance or routing to alternatives, which keeps it below a 5.

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