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

The annotations already establish read-only, idempotent, non-destructive, closed-world behavior. The description adds useful context by saying results are computed with astronomical algorithms and by enumerating the returned values and capability limits, though it does not discuss calculation accuracy or timezone edge cases operationally.

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 front-loaded with "Use this when" and then proceeds through return contents and exclusions in a compact, scannable structure. Every sentence contributes either usage context, capability boundaries, or output expectations.

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 an output schema and informative annotations already covering much of the contract, the description supplies the remaining intent, exclusions, return summary, and usage contexts needed for correct invocation. No major ambiguity remains for an agent deciding whether and how to call it.

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 100%, so city, dates, month, and labels are already fully documented in the input schema, which sets the baseline at 3. The description reinforces likely usage through birthday, couple, and monthly-calendar examples, but it does not add syntax or constraints beyond what the schema provides.

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 states a specific resource and outcome, including returned fields such as phase name, illumination, moon age, and exact phase times. It excludes adjacent domains like astrology, tides, moonrise, planets, and eclipses, but it never names or directly contrasts the sibling tools generate_moon_poster and generate_star_map, so sibling differentiation is only implicit.

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 explicitly lists when to use the tool: birthday/wedding/first-date moons, today or tonight, couple comparisons, and monthly calendars. It also lists clear exclusions, but it does not explicitly route related requests such as a moon poster to the sibling generate_moon_poster.

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