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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds genuinely new behavioral context: the output is AI-written rather than purely computed, it is ephemeris-grounded, and it explicitly discloses a 50-credit Tier 3 cost that appears nowhere in the structured fields.

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?

Two short sentences with the core purpose front-loaded, followed by compact group/cost metadata. Nothing is padded, though the bracketed metadata is administrative rather than agent-facing guidance.

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 values needn't be explained, and the generation intent is clear. However, for a 6-parameter tool with mostly undocumented optional parameters (language, fields, precision, disclaimer_inline), the description leaves an agent without enough context to drive those options correctly.

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 only 33% (date, sign, language and disclaimer_inline have no schema descriptions), so the description was expected to compensate and does not — it never mentions language, fields, precision, or date semantics. The two documented params are covered only by the schema itself.

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 ('Generate a weekly horoscope') and pins the scope with '(7-day window)', which implicitly separates it from the daily/monthly/yearly siblings. It stops short of naming those alternatives explicitly, so differentiation relies on the agent noticing the time-window wording.

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?

There is no guidance on when to pick this over astroway_horoscope_daily, _monthly, or _yearly, and no prerequisites or exclusions. Usage is only implied by the word 'weekly'; the agent must infer the selection rule from the sibling names.

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