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

No annotations are present, so the description carries the full burden. It adds a valuable non-obvious behavior: illumination and lunar day are computed from the real Sun-Moon conjunction rather than the mean synodic formula, with an explicit warning about discrepancies of hours or even a whole lunar day. This is genuinely helpful, though it leaves output format and timezone handling implicit.

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?

Two dense sentences with no filler. The first sentence front-loads the core outputs, and the second explains the important calculation caveat. Every clause earns its place.

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 no output schema and no annotations, the description reasonably covers the returned quantities and a key behavioral caveat. However, it does not describe the return structure, how local time and timezone offsets interact with the 'given moment', or how this tool relates to sibling tools. These gaps are notable but not critical for a basic call.

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 the baseline is 3. The description does not add parameter-level details beyond what the schema already provides, though the phrase 'for a given moment' loosely connects to the date/time/tz_offset_minutes parameters. No additional syntax, constraints, or examples are supplied.

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 clearly enumerates what the tool provides: Moon phase, illumination, lunar day, sign and degree for a given moment. It lacks an explicit verb, but the resource and outputs are immediately identifiable. It does not name sibling tools, so some differentiation must be inferred.

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 guidance on when to choose this tool over siblings such as planet_positions or aspect_exact_time. No conditions, exclusions, or alternatives are mentioned. An agent must rely on the tool name and output list to infer appropriate use.

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