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

Annotations already cover the read-only/idempotent/non-destructive profile, and the description adds real value on top: it discloses that retrograde re-entries and uncertainty windows appear in results, that the interval is UTC half-open with a 400-day cap, and that no birth data is stored or logged. It lacks detail on output shape, but the output schema covers that.

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 query examples, then constraints, then the privacy statement. The multi-language examples are slightly repetitive but earn their place by illustrating natural-language query patterns; no filler sentences.

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 an output schema present, return values need not be explained, and the description covers the key behavioral facts (retrograde re-entries, uncertainty windows, date bounds, privacy). Missing only guidance on planet selection breadth relative to sibling tools, which is a minor gap.

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 25%, so the description must compensate. It adds meaning for the date parameters ('[from,to) UTC, max 400 days') but says nothing about planet enum values or the lang fallback that the schema only partially documents. Partial compensation warrants a mid score.

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 (find) and resource (when a planet enters a zodiac sign), reinforced by three concrete example queries across languages. The event-based framing ('when does Venus enter Leo') clearly separates it from sibling planetary-position and retrograde-period tools.

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 context is implied through examples and the 'max 400 days' date-window constraint, plus a note that retrograde re-entries are included. However, it never states when to prefer this over get_retrograde_periods or get_planet_positions, leaving alternative selection to inference.

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