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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: an authentication prerequisite (the customer must be logged in) and a data-freshness rule (game contents only surface once revealed, otherwise only the reveal date is shown). That is real added value, though it does not address error/empty states.

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?

It is front-loaded with the precondition, then the returned fields, then the read-only/where-to-change note, then the auth requirement — a logical order. It is a dense 3-sentence block with a UI cross-reference ("Tu cuenta > BOX") that earns its place by anchoring expectations, though a little is spent restating read-only status already covered by annotations.

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 no output schema and a read-only, 1-param ancillary tool, the description carries the return-value burden and does so: it enumerates modalities, per-box fields and the reveal-timing caveat. Combined with the auth requirement, an agent has enough to call it correctly; only edge cases (not subscribed, FR vs ES differences) are left implicit.

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% for the single 'country' parameter (enum es/fr, with its effect on language, prices and links already documented in the schema). The description never mentions country or any parameter behavior, so the baseline of 3 applies — nothing added, nothing lost.

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?

It states a specific resource (Zaca+ Box subscription) and exactly what is returned: active modalities (Familiar, Para 2, Outlet) plus, for each, the next box's name, ship date and max price. That is far more than a restatement of the name/title. It does not explicitly differentiate itself from the nearby sibling 'club_and_box', so it falls 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?

It names the triggering condition ("Si el cliente está suscrito a Zaca+ Box") and states what the tool does NOT handle (sign-up, cancellation, modality changes happen in the customer's account via manage_url), which effectively routes those actions elsewhere. It does not explicitly say when to pick this over my_club or club_and_box, so it is clear context without explicit alternatives.

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