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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds real context beyond them: NASA catalogue source, pinned ephemeris, geocentric alignment rather than greatest-shadow or local-time conventions, and explicit clipped coverage. It says nothing about ordering or truncation behavior when results exceed the day window, but the substantive methodology disclosure is valuable.

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 core capability and scope are front-loaded in the first sentence, and the remaining sentences each add a distinct constraint rather than restating. 'Clipped coverage is explicit' is terse to the point of opacity, but the overall density is 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 a rich annotation set and an output schema, the description need not explain return values and correctly avoids doing so. It covers data source, temporal range, timezone requirement, and negative scope, leaving only minor gaps around the date parameter and what 'clipped coverage' concretely means.

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 only 33%, so the description must carry weight. It adds meaning for two of three parameters: 'one to 366 civil days' clarifies the days window, and 'supplied viewing timezone' plus 'not inferred birthplace or current location' clarifies timezone intent. The date parameter's semantics and the 'today' sentinel are left 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?

States a specific verb and resource: returns catalogue-confirmed solar and lunar eclipses, with dates and types resolved into the supplied timezone and a bounded 1-366 day window. The scope is unambiguous on its own, though no sibling tool is named to contrast against.

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 definition sets boundaries (no birth details, no personal match, no local visibility calculation) which implicitly tell an agent this is a global catalogue lookup rather than a personalized timing tool. However, it never explicitly says when to pick this over the timing or overview siblings, leaving routing to inference.

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