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

Annotations already declare readOnly/idempotent/non-destructive, so the description is free to add real value: it says the response is the full text for the day, that dates are in Dutch time, and that a link to the page is included. That is useful return-content context beyond the annotations, though nothing is said about missing dates or failure behavior.

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?

A single front-loaded sentence covering resource, scope, date semantics, and return payload with no filler. Every clause earns its place.

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?

With no output schema, the description still tells the agent what comes back (full daily text plus page link), and annotations carry the safety profile. Only edge cases such as an unavailable date or a future date beyond the published range are unaddressed.

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%, so baseline is 3, but the description adds meaning the schema lacks: the date is interpreted in Netherlands time and the default is 'vandaag'. The sign enum's language-mapping hints live in the schema and are not repeated, which is correct.

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-and-resource: fetch the daily horoscope text for a zodiac sign, for today or a chosen date, plus the page link. The 'dag' granularity inherently separates it from weekhoroscoop/maandhoroscoop/jaarhoroscoop, though no sibling is named explicitly.

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 implied by the 'daghoroscoop' scope and the note that an empty date means today, but there is no explicit statement of when to pick this over week-/maand-/jaarhoroscoop or other siblings. An agent must infer the routing from names alone.

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