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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile needs no restating. The description adds non-obvious behavioral detail the annotations do not carry: daily values are computed at a fixed 12:00 local time and the four event times are expressed in the requested time zone, which materially affects how results should be interpreted.

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?

It is a single compact sentence with no filler, and the key scope ('every day of a month') is front-loaded. The sentence is long and stacks two payloads (daily rows and event times), so a split could aid scanning, but nothing is wasted.

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?

Return values need not be explained because an output schema exists, and the three optional parameters are fully documented in the schema. The description covers granularity, time basis and scope, leaving only minor unknowns such as response size for a full 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% (year bounds 1900-2100, month 1-12, IANA time zone, all with default behavior), so the baseline is 3. The description goes slightly beyond it by tying the time zone parameter to two distinct effects: the local-time basis of the daily readings and the zone in which the event times are reported.

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 opens with a concrete verb and resource ('Returns every day of a month') and enumerates the payload: daily phase and percent lit plus the exact times of the four principal lunar events. That scope (a whole-month calendar of daily values plus event timestamps) is specific enough to separate it from single-point siblings like get_moon_phase or find_full_moons, though it never names an alternative to confirm the boundary.

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 scope wording: an agent can infer this is the tool for a month-long calendar rather than a single instant. There is no explicit when-to-use statement, no exclusions, and no pointer to the sibling tools for phase-at-a-moment or distance queries.

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