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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds that it reports the last aspect and the sign ingress, which is useful output context, but says nothing about auth, rate limits, or computation caveats.

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?

A single front-loaded sentence stating the check and its outputs, followed by compact group/cost tags. Efficient and free of filler, though the return-value clause partially duplicates what the output schema already provides.

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?

Annotations and the output schema carry much of the burden, but for a 15-parameter tool with low schema coverage the definition is thin: no sibling differentiation, no guidance on timezone/location handling, and no usage context. It is minimally viable rather than complete.

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 only 33% across 15 parameters, and the description supplies zero parameter guidance. Nothing explains the required date/time/latitude/longitude quartet, the timezone-vs-timezoneOffset choice, or the compact-mode fields/precision options, so the description fails to compensate for the coverage gap.

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+resource ('Check if the Moon is void-of-course') and scopes it to 'this horary chart', which implicitly separates it from the range-scanning sibling astroway_calendar_moon_voc. It also states the return content (last aspect, next sign ingress). It stops short of explicitly naming the alternative tool, so an agent must infer the distinction.

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?

There is no when-to-use guidance: nothing says to prefer this over astroway_calendar_moon_voc, astroway_stream_void_of_course, or the webhook variant. No prerequisites (e.g., that a specific moment and location are needed to build the horary chart) are stated.

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