Moon Void-of-Course

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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the safety profile is fully covered there. The description adds genuine value by defining what a VOC window is, which is what determines the shape of the returned periods. It omits the practical constraint that rangeDays caps at 366 days, and that the cost is 10 credits, but the latter appears in the metadata block.

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?

Two well-structured sentences: the first states the action and scope, and the second defines the key term. The trailing bracketed metadata block is boilerplate, but it is structured and skimmable. Almost nothing is wasted.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. What is missing is practical calling information: what date and time represent (an anchor? a window start?), the rangeDays limit, and how this tool relates to the two overlapping VOC tools. That leaves gaps for a 5-parameter calendar tool.

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 40%. timezone and timezoneOffset are richly documented in the schema, but date, time, and rangeDays have no schema descriptions. The description says 'within a date range' but never explains whether date and time anchor the start of the search window, and it never explains the 366-day cap on rangeDays. It only partly compensates 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?

States a specific verb ('Find') and resource ('Moon void-of-course periods') and then defines the concept precisely: 'from its last aspect until it enters the next sign.' That definition goes beyond the name. It does not distinguish itself from siblings that overlap conceptually (astroway_stream_void_of_course for alerts, astroway_horary_moon_voc for horary work).

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 description implies usage by scoping the tool to a date range. However, it never says when to prefer this tool over astroway_stream_void_of_course (ongoing VOC alerts) or astroway_horary_moon_voc, which is the most likely confusion given the near-identical name. The agent also gets no guidance on when the tool is not appropriate.

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