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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds useful output context about day-by-day phase and illumination data, but does not describe pagination, timezones, or response fidelity beyond that.

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?

The description is short and front-loaded: a clear actioning first sentence and a pragmatic use-case second sentence. It is efficient, though the second sentence is phrased more like marketing than operational guidance, so a 5 is slightly too high.

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?

Given the read-only nature and the fully self-documenting param schema, the description is almost sufficient. It tells the agent the response content (phase/illumination for each day), even with no output schema, but it does't specify per-day field names or common alternatives such as timezones or date formatting.

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 100% with detailed explanations, defaults, ranges, examples, and enum values. The description doesn't need to repeat parameter details, so it earns the baseline 3.

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 states a specific resource ('complete lunar calendar'), the scope ('every day of a specific month'), and what it contains ('moon phase and illumination'). This month-scoped behavior distinguishes it from the current/upcoming moon-phase sibling tools.

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 description gives clear use context: 'creating moon phase calendars, lunar planners, and astrology event schedules.' It does not explicitly name alternative sibling tools or provide when-not-to-use guidance, so it falls just short of a 5.

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