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 genuinely new context — the GET endpoint path and a billing note that this endpoint is absent from the public credit manifest — but says nothing about error behavior for an unknown slug or what the response envelope looks like.

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?

A single front-loaded sentence followed by four scannable bracketed metadata lines; nothing is buried and nothing is padded. The only mild redundancy is the '[Required: slug]' line, which duplicates the schema.

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 a rich annotation set, a full output schema, and 100% parameter documentation, the description supplies the remaining operational facts (endpoint, group, billing caveat). The one gap for an agent is discoverability: how to get a valid slug and why this is preferable to the draw or interpret 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 100%, including the 'lowercase and hyphenated' constraint on slug and the compact-mode meaning of fields and precision, so the schema carries the burden. The description adds no parameter meaning of its own beyond repeating that slug is required, which is the expected baseline-plus for a fully documented schema.

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 states a specific verb and resource — 'Single Marseille card lookup by slug' — which separates it from the plural listing tool astroway_tarot_marseille_cards and from the draw/interpret siblings. It is clear without naming an alternative explicitly, so it lands just short of a 5.

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 guidance on when to use this instead of astroway_tarot_marseille_cards, astroway_tarot_marseille_majors, or astroway_tarot_marseille_interpret, and no hint that a listing call is the normal way to obtain a valid slug. The only usage-adjacent content is a restatement that slug is required.

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