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

Annotations already declare readOnlyHint/idempotentHint, so safety is covered. The description usefully adds the shape of the result and the '[Cost: 50 credits (Tier 3)]' charge, but says nothing about auth, rate limits, or response size behavior. Adequate-but-thin against annotation coverage.

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?

One front-loaded sentence covering purpose and outputs, followed by compact group/cost metadata. No filler, though the bracketed metadata lines are boilerplate rather than description content.

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 need not be described. However, with 6 parameters, low schema coverage, and no usage guidance, the description leaves an agent guessing about language/disclaimer_inline and about when this tool beats its many siblings.

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%: language and disclaimer_inline have no descriptions, and sign1/sign2 are bare enums. The phrase 'between two charts' loosely implies the two required sign parameters but adds no format, default, or interaction detail to compensate for the gap.

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?

Specific verb+resource: 'Generate a relationship horoscope based on synastry between two charts', with concrete outputs named (strengths, friction points, 30-day themes). The two-chart synastry scope implicitly distinguishes it from the single-sign time-period siblings (daily/monthly/weekly/yearly), but 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?

No when-to-use or when-not-to-use guidance, no prerequisites, and no routing to alternatives such as astroway_render_composite or astroway_horoscope_daily for period-based readings. Usage is only inferable from the purpose sentence.

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