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

Annotations already declare readOnly/non-destructive/non-open-world, so the safety profile is covered. The description adds genuinely useful behavior the annotations cannot convey: the returned fields, that results are localized, and that spread ids are language-invariant, which prevents needless re-listing per locale.

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?

Two sentences, zero filler, with the payload content stated first and the draw_cards linkage as the closing, high-value note.

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?

Return values are documented by the output schema, safety by annotations, and the one parameter fully by the schema; the description supplies exactly the missing cross-tool context. Nothing needed to invoke it correctly is absent.

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% and the locale enum already documents every value and the zh-CN/zh-TW distinction, so the baseline is 3. The description's 'in the requested language' and 'ids are the same in every language' hint at locale behavior but add no format detail beyond the 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?

Specific verb+resource (list the tarot spreads) plus the exact fields returned, and it explicitly ties itself to the sibling by stating the ids are the values draw_cards accepts as spread_id. An agent can distinguish it from draw_cards purely from the text.

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?

Strong implicit routing: the note that ids are draw_cards' spread_id tells the agent this is the discovery step before drawing. However, it never states an explicit when-to-use/when-not condition, so it stops short of full guidance.

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