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

Annotations already cover the safety profile (readOnly, idempotent, not destructive, closed world), and the description layers on substantial extra behavior: no merchant links are returned, prices_from excludes stale offers and reflects only general-segment rows, has_free_item semantics, and the user_navigation handoff rule with an explicit prefetch prohibition. This is context an agent could not derive from annotations alone.

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?

Purpose is front-loaded, but the body is a single sprawling sentence that piles return fields, filter caveats, and handoff rules together. The filter enumeration largely duplicates the schema, so not every clause earns its place, though the information density is high.

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, the description carries the full burden and discharges it: it enumerates returned fields (title, kind, source, state, dates, deadline_status, prices_from, discount, brands, categories, sample products), explains prices_from/has_free_item edge cases, and clarifies canonical_page vs site_entry_page. Nothing an agent needs to interpret results or call correctly is missing.

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 86%, so the schema already documents each parameter; the description only restates the filter names and the 'running by default' behavior that the schema spells out. It adds no slug format, enum nuance, or cursor semantics beyond what is structured, so the baseline of 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 verb and resource ('Lists the sales and campaigns recorded by a Japanese music-production buying guide'), gives the ordering ('running ones first'), and explicitly distinguishes itself from get_current_offers, which returns offers for one product. An agent can identify the tool without opening the schema.

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?

Names the sibling alternative (get_current_offers) and the condition that selects it, and lists the filter surface (brand, category, kind, source, state, limit, cursor). It stops short of stating when-not to use this tool or how campaign browsing differs from the other siblings, so it is clear context rather than a complete routing rule.

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