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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the description's added value is in scope limits: a hard 2020–2035 date range, timezone handling with Polish time as default, and eclipse visibility computed from Warsaw — a location-bound constraint the agent could not know otherwise. It does not discuss result size or how many entries a busy month may return.

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 dense sentence, but it is front-loaded with the core scope ('events of a month') before the enumeration, and every clause contributes concrete content. It is somewhat packed with semicolon-separated lists, though nothing is redundant.

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 and full annotation coverage, the description only needs to convey scope and limits, which it does: date range, default timezone/language, and the Warsaw visibility caveat. The one remaining gap is the absence of any hint about output volume or ordering of the listed events across the month.

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 100%, so all four parameters are already documented with defaults and enum values. The description only restates defaults (Polish time, optional Moon sign listing) without adding format hints or edge-case behavior beyond the schema, which is the expected baseline.

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 the exact resource (a month's astrological events) and enumerates its contents precisely: lunations with signs, ingress of the Sun and planets, retrograde stations and periods, eclipses with visibility, and optional Moon sign changes. This distinguishes it from siblings like sky_at (a single moment) and sign_dates (sign boundaries) without the agent needing to open any schema.

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?

Usage is only implied by the content list — an agent can infer this is the tool for month-long event listings rather than a single-moment snapshot. There is no explicit when-to-use/when-not statement and no naming of sky_at or sign_dates as alternatives.

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