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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds the result-bounding rule (aspects only until sign exit) and the metadata block discloses a real behavioral trait not in the schema — cost of 20 credits (Tier 2) and the POST endpoint. It says nothing about auth, rate limits, or error behavior.

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?

One dense, front-loaded sentence gives purpose and scope immediately, and the bracketed metadata block is scannable rather than prose. No filler sentences; only the lack of any alternative/comparison sentence keeps it from a 5.

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 present, the description need not describe return values, and annotations cover the safety profile. However, for a 15-parameter chart tool sitting among five horary siblings and a near-identical astroway_calendar_moon_aspects, the definition leaves sibling selection and the ayanamsa/zodiac/house-system configuration entirely unexplained.

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 compensation burden it does not meet. It contributes only the required list (date, time, latitude, longitude), while ayanamsaId, zodiacType, houseSystem, cosmogram, city and name remain undocumented in either place, and nothing explains how the chart-defining inputs shape the returned aspects.

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 (list), a specific resource (Moon aspects), and a precise scope constraint (before the Moon leaves its sign), plus a role label (key timing tool in horary). This clearly separates it from astroway_horary_moon_voc (void of course) and astroway_horary_diagnostics, though it does not name those siblings.

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 key timing tool in horary" implies when the tool is appropriate, but there is no explicit when-to-use/when-not guidance, no statement of alternatives, and no prerequisites (e.g. that this is a standalone horary chart cast for the question moment). Usage is inferable rather than instructed.

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