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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed world), so the bar is lower. The description does add one genuinely useful behavioral fact beyond them: the response is a summary (title + core) plus a link, not the full horoscope text — relevant because no output schema exists.

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 with no filler; the resource and return shape come first. It is efficient, though it leaves room for a short routing clause without becoming bloated.

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 simple two-parameter read tool with complete schema coverage and no output schema, the description covers what it returns and the scope. The only meaningful gap is the absence of any comparison to the sibling day/week/month horoscope tools.

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 both parameters are fully documented in the schema, including the 2026/2027 range, the 'empty means this year' default, and the Dutch sign enum with translation hints. The description adds nothing beyond that, so the baseline 3 applies.

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?

Names a specific resource — the yearly horoscope for one zodiac sign — and states what comes back (title plus core text and a link to the full horoscope). The period word 'jaar' implicitly separates it from daghoroscoop/weekhoroscoop/maandhoroscoop, but that distinction is never made explicit.

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 tool name and period word; there is no explicit 'use this when the user asks for an annual reading, not a daily/weekly one' routing. With three sibling horoscope tools at other periods, an explicit exclusion sentence would materially help selection.

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