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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds real behavioral detail beyond them: the exact degradation when time is missing (houses, angles, sect set to null) plus a timeUnknown block reporting the Moon's range for the day, and the ?lang= localization effect.

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?

Front-loaded with the core purpose, then the single most important edge case, with no filler. The text is visibly truncated mid-sentence ('adds localized: pl…'), which prevents judging whether the tail is as economical as the head.

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 re-explained, and the description does cover the key null-time branch. But for a 16-parameter astrological tool at 31% schema coverage, the many unexplained configuration parameters (house system codes, zodiac type, sidereal school, cosmogram, compact fields/precision interplay) leave real gaps for correct invocation.

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 31%, so the description needs to compensate and only partly does: it explains timeUnknown and lang, while parameters like zodiacType, houseSystem, cosmogram, city, name, ayanamsaId and the enum codes receive no explanation in either place. The schema does carry decent prose for fields, ayanamsa, timezone, precision and timezoneOffset, which supports a baseline 3 but no higher.

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 and resource ('Calculate a full natal chart') and enumerates exactly what is produced (planets, house cusps, aspects, sect, angular data), so the agent knows the payload without opening the schema. It does not, however, differentiate itself from close siblings such as astroway_western_planets or astroway_western_ephemeris, which keeps it out of the top band.

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?

Gives a concrete when-to-use branch: when the birth time is unknown, send timeUnknown: true instead of time, with a clear statement of the resulting response shape. It provides no guidance on choosing this tool over the other natal/ephemeris siblings or on when each house system or zodiac type applies, so it stops short of explicit alternative routing.

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