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 description earns credit for adding the return payload (tropical geocentric positions, retrograde flags, Moon phase/illumination) and defaults (now, UTC). The no-logging/no-storage statement adds a privacy guarantee, though it is slightly odd since the tool accepts no birth data at all.

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 returns, then defaults, then the privacy note — a logical order with little waste. The multilingual example list is somewhat bulky for the value it adds.

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, return fields need not be enumerated, and annotations cover safety. The description additionally supplies defaults and a data-handling guarantee, leaving only edge cases (invalid datetime, large-range behavior) unaddressed.

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 coverage is only 33% (only lang is documented), so the description must compensate. "Defaults to now and UTC" does cover the datetime and timezone defaults, but it adds nothing about accepted ISO-8601 format nuances, timezone identifiers, or why lang matters, leaving two of three parameters thinly specified.

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 (compute) and resource (current sky / planet positions at an ISO instant), plus concrete example queries in two languages. However, it never distinguishes itself from the overlapping sibling get_moon_phases, which it partly duplicates by returning Moon phase/illumination.

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?

"Compute the current sky or a specified ISO instant" plus the natural-language examples ("where is Venus today", "cielo di oggi") make the intended context clear and imply it defaults to now. No exclusions or named alternatives (e.g. "for a full natal chart use calculate_birth_chart") are given.

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