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

Annotations already declare the operation safe (readOnlyHint, idempotentHint, destructiveHint=false, closed-world), so safety needs no elaboration. The description does add genuinely useful behavioral context not present in the structured fields: the credit cost and tier. It says nothing about reversal handling or randomness despite the seed/allowReversed parameters.

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 spread structure is front-loaded in a single tight sentence, with the group and cost tags clearly demarcated. It is efficient and wastes no words, though the sparseness reflects under-specification as much as discipline.

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 cost tag covers a key operational fact. However, with five parameters at 40% schema coverage and no usage guidance, an agent still lacks enough to invoke this confidently versus its many 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 coverage is 40% — only `fields` and `precision` carry descriptions — and the description adds no parameter meaning at all. `seed`, `question`, and `allowReversed` remain unexplained in both places, and the description does not compensate for that gap.

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 concrete deliverable — a 13-card spread broken into 12 months plus a theme card — which is more specific than a bare restatement of the title. It does not, however, distinguish this spread from the many sibling draws (celtic cross, horseshoe, three-card, etc.), so an agent must rely on the tool name to route correctly.

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 statement of when to use a year-ahead spread versus any of the other RWS draw tools, and no exclusions or prerequisites. The agent is given the shape of the output but nothing about the situation that should trigger this tool.

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