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

With no annotations, the description discloses useful behavioral details: the year range is limited to 1900–2100, and output includes exact UTC times and moon signs. It implies a read-only listing operation. It doesn't specify error handling or return formatting, but for a simple list tool this is adequate.

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 a single sentence that is directly front-loaded with the action ('List') and packs in the resource, time range, and output details without any redundancy or filler. Every word contributes value.

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?

For a tool with a single required parameter and no output schema, the description is sufficiently complete. It covers the primary function, the time constraint, and the key aspects of the returned data. There are no significant gaps for the intended use case.

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?

The schema already describes the 'year' parameter, but the description adds a critical constraint not present in the schema: the acceptable range 1900–2100. This enhances parameter understanding beyond the schema, justifying a score above the baseline of 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 uses a specific verb 'List' with a clear resource 'every new moon of a year' and specifies the year range (1900–2100) and output details (exact UTC times and moon signs). It naturally distinguishes itself from sibling tools like list_full_moons and get_moon_phase, leaving no ambiguity about its function.

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 purpose is clear enough to understand when to use it: when a list of new moons for a given year is needed. However, there is no explicit mention of alternatives or exclusions, such as 'use get_moon_phase for a single phase' or 'use list_full_moons for full moons', so it falls short of a full 5.

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