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 the endpoint and a cost figure (10 credits, Tier 1), which is genuinely useful operational context, but it says nothing about response shape or pagination beyond what the output schema gives.

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 and tight: the distinguishing deck conventions come first, followed by compact bracketed metadata. No wasted prose, though the domain trivia is arguably more than a selection decision requires.

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 parameterless, read-only catalog call with an output schema, the definition is minimally sufficient. It still leaves unresolved how this full-deck tool relates to the slug, majors, and other Marseille siblings, which is the main thing an agent would need to choose 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 coverage is 100% and both parameters (fields, precision) are fully documented in the schema, so the baseline of 3 applies. The description adds nothing about the compact-mode projection or precision handling, though its note about pip-minor interpretation is relevant to the returned data.

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 asserts domain facts about the deck (78 cards, Justice=8/Strength=11, pip minors by number+suit) but never states the tool's action — that it returns the full Marseille card catalog. The name and title carry the verb, so an agent can guess, but the description itself is a content blurb rather than a statement of purpose.

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 guidance and no mention of alternatives, despite many near-neighbours (astroway_tarot_marseille_cards_slug, astroway_tarot_marseille_majors, astroway_tarot_decks, astroway_tarot_rider_waite_cards). Nothing tells the agent when to pick this full-deck listing over a single-card lookup.

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