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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuine extra context: the reduction method used and the 10-credit Tier 1 cost, which is useful billing behavior. It does not describe the result shape, but an 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?

One dense sentence front-loads the substance, with group and cost as bracketed metadata rather than prose. Nothing is wasted, though the metadata tags consume roughly half the visible text.

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 one-required-parameter deterministic computation with an output schema, the description covers purpose, method and cost adequately. The notable gap is sibling disambiguation across a very large tarot family, which is exactly what a birth-card tool must resolve.

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 67%: fields and precision are documented in the schema, while date has only a pattern and no prose. The description adds the conceptual meaning of date (a birth date whose components are reduced) but no format or edge-case guidance beyond what the pattern already supplies.

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 the specific output (a birth card) and the exact derivation method (Mary Greer's m+d+y reduction), which distinguishes it from astroway_tarot_marseille_birth_card (different deck) and astroway_tarot_rider_waite_year_card (different formula). The verb is implicit rather than stated, so it falls short of a perfect verb+resource statement.

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 when-to-use guidance and no mention of alternatives, despite the sibling set containing several adjacent card-derivation tools (year_card, soul_personality_card, shadow_card, marseille_birth_card). The agent must infer selection from the name alone.

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