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

Annotations already declare readOnly/idempotent/non-destructive and closed-world, but the description adds real value beyond them: the [from,to) UTC range semantics, the 400-day maximum, the fact that output is in local times with signs and uncertainty, and an explicit no-store/no-log privacy guarantee.

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?

Front-loaded with purpose and examples, then operational constraints, then privacy. The multilingual example strings add some bulk but usefully signal non-English intent; overall dense but each sentence serves a purpose.

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, so return-value explanation is unnecessary, and the description focuses on the operational constraints (range, timezone, max span) that the schema does not express. Coverage is strong; the notable omission is explicit guidance on the optional lang parameter's fallback behavior beyond its schema note.

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?

With only 25% schema description coverage, the description carries meaningful load: it names from_date, to_date and an IANA timezone, and adds constraints the schema lacks (inclusive/exclusive range semantics, 400-day cap, UTC boundary interpretation). Only 'lang' semantics go undocumented in the description, relying on its schema note.

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?

States a specific verb ('Calculate') and resource (new/first quarter/full/last quarter Moon), and backs it with concrete example queries. An agent can distinguish this from all astrology siblings (birth charts, transits, signs) without opening the schema.

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 example queries ('when is the next full Moon', Italian equivalents) clearly frame the intended use case. It does not, however, explicitly name when to prefer it over a sibling or state exclusions, so it stops short of full routing guidance.

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