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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered. The description adds a genuinely useful behavioral detail in the '[Cost: see your plan — endpoint not in the public credit manifest]' line, but it doesn't disclose anything about return payload or latency, so it is a modest addition rather than rich transparency.

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?

The single-line purpose is front-loaded and the bracketed metadata lines are terse and scannable. There is some redundancy between the endpoint line and the description, but nothing is wasteful enough to hurt readability.

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 full input schema, an output schema, and annotations covering the safety profile, the definition only needs to add routing and cost context, which it partially does. The cost note is vague ('see your plan') and no alternative is named, leaving a small gap for an agent choosing among the numerous tarot 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%, so slug, fields, and precision are already documented in the schema itself. The description only repeats '[Required: slug]' and adds no syntax, format, or usage nuance beyond the structured fields, so baseline 3 is appropriate.

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 clearly states the resource (a single Marseille spread) and its scope via the word 'single', which implicitly contrasts with the sibling list tool astroway_tarot_marseille_spreads. However, it uses a noun phrase ('Definition of...') rather than a verb and never explicitly names the list alternative, so the differentiation relies on inference rather than direct contrast.

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, no exclusion conditions, and no named alternative. The only usable cue is the bracketed '[Required: slug]' line, which implies you need a known slug but does not tell the agent when to prefer this tool over the spreads list or the draw_* tools.

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