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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely useful operational context — the POST endpoint and the 10-credit Tier 1 cost — which an agent cannot get from annotations or schema, but it says nothing about the returned payload or whether the cost is incurred per call.

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 — one descriptive sentence plus a compact structured metadata block with endpoint, required param and cost front-loaded. Nothing is padded, though the metadata block repeats facts (group, endpoint) that add little selection value.

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 explained, and the read-only/cost facts are present. However, for a tool sitting among dozens of overlapping tarot computations, the absence of any deck/method selection guidance or alternative routing leaves the definition only minimally complete.

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 75%, with art, fields and precision each documented in the schema itself; the description only restates that date is required, matching the schema's required list. It adds no format or interpretation detail (e.g., how a date maps to a card) beyond structured data, so the baseline 3 applies.

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 a specific resource (a birth card) and method (Greer) plus the deck (Marseille), which usefully separates it from the sibling astroway_tarot_rider_waite_birth_card. It does not explain what a 'birth card' actually is or how it is derived, so a wholly uninformed agent still has a small gap, but the verb+resource is identifiable.

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 context and no routing to alternatives such as astroway_tarot_marseille_year_card or the Rider-Waite birth card. The only usage cue is the bare 'Required: date' line, which is schema information rather than guidance.

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