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

Annotations already declare readOnlyHint, idempotentHint, false destructiveHint, and openWorldHint=false, so the safety profile is fully covered and the description need not restate it. The description does add genuinely non-schema information: the returned content (last aspect made, time of next ingress) and a 10-credit Tier 1 cost, which matters for call budgeting. It stops short of disclosing computation caveats, such as whether the result is sensitive to the supplied location or timezone.

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 sentence is front-loaded and states the check and the returned values with no filler. The bracketed metadata lines (group, endpoint, required, cost) are compact and scannable rather than verbose prose, though the 'Required' line restates the schema redundantly.

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 the return shape does not need explaining, and annotations cover the safety profile. However, for a tool with 15 parameters and multiple interacting configuration options (timezone vs. timezoneOffset, ayanamsa vs. ayanamsaId, tropical vs. sidereal), the description leaves the agent without guidance on which knobs matter for a horary Moon VOC query.

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, so the description carries a heavier burden and does not meet it. It lists only the four required fields (date, time, latitude, longitude), which duplicates the schema's 'required' array, and says nothing about the eleven optional parameters, notably timezone, ayanamsa, zodiacType, houseSystem, or the compact-mode fields/precision controls.

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: it checks whether the Moon is void-of-course and returns the last aspect plus the time it enters the next sign. That is a concrete, verifiable operation an agent can match to a question. It does not, however, distinguish this from sibling tools such as astroway_calendar_moon_voc or astroway_stream_void_of_course, which appear to compute closely related results.

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 explicit when-to-use guidance, no exclusions, and no named alternative. The only contextual signal is the '[Group: Horary]' tag, which implies a horary-consultation context but never states that this tool should be chosen over the calendar Moon VOC or the void-of-course streaming sibling.

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