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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so safety is fully covered. The description adds one genuinely useful operational fact the annotations do not carry: the 10-credit (Tier 1) cost. It still says nothing about whether the response is a static reference list or a draw, but with annotations doing the heavy lifting a 3 is apt.

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?

Extremely tight and front-loaded: the resource is stated first, then group and cost metadata. Nothing is wasted, though the brevity comes at the cost of omitting any disambiguating context.

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 a large family of Marseille tarot siblings, the definition is incomplete on the one thing that matters most here: how this reference lookup differs from marseille_cards, cards_slug, and the draw_* 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?

Both parameters (fields, precision) are optional compact-mode controls with 100% schema description coverage, so the schema already explains them fully. The description adds no parameter meaning beyond that, which is the baseline-3 case when schema coverage is high.

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?

The description names a specific resource (the 22 Major Arcana) scoped to the Marseille deck, so an agent knows this returns that fixed subset rather than the full deck. It does not, however, differentiate itself from close siblings such as astroway_tarot_marseille_cards or astroway_tarot_marseille_cards_slug, so the agent must infer the boundary from the names alone.

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 explicit when-to-use guidance and no named alternative. Given near-identical siblings (marseille_cards, marseille_cards_slug, rider_waite_majors), the description should say when to pick the Marseille majors lookup versus the full card list, but it offers nothing.

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