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

The annotations already declare readOnly, idempotent, non-destructive and closed-world behavior, so the safety profile is fully covered. The description adds useful context (UK time zone, per-event extra fields, filterable special events) but does not mention ordering guarantees, default window behavior, or pagination, which is acceptable for a read-only query tool with annotation coverage.

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 sentences, the return contents are front-loaded and the special-Moon capability is stated last. No filler, though the trailing sentence about special Moons is slightly vague in phrasing ("listed on their own").

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 and the parameter schema is fully documented, so the description only needs to frame scope and content, which it does. It stops short of explaining how this tool relates to the other Moon tools, which is the remaining gap for an agent selecting among seven siblings.

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% and each parameter is well documented with defaults and limits, so the baseline is a 3. The description goes slightly beyond the schema by establishing the UK-time/UK-date frame that contextualizes the `from`/`to` dates and by clarifying that special-Moon filtering fixes the phase, which helps an agent combine the `phase` and `special` parameters correctly.

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?

"Returns the dates and UK times of upcoming full, new, first quarter and last quarter Moons" is a specific verb and resource with the returned fields enumerated (traditional name, distance, supermoon/blue/micromoon/black Moon flags). It is clear what the tool produces, but it never names or distinguishes itself from close siblings such as get_moon_calendar or get_moon, which an agent would need to choose between.

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?

"Special Moons can be listed on their own" implies the `special` filter exists for targeted lookups, and the emphasis on dates/times suggests a calendar-style listing. However, there is no explicit when-to-use or when-not-to-use guidance relative to get_moon_calendar, list_eclipses, or get_moon, so the agent must infer selection.

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