Megamarket Product Card

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the bar is lower. The description adds genuinely new context by enumerating failure modes (BadRequestError, NotFoundError, TransportDownError, ParserDriftError), which tells the agent how this tool can fail and why.

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 opening sentence is front-loaded and tight, and the error-format block earns its place. The Return Format block largely restates the output schema fields, which the description need not duplicate, adding mild redundancy.

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 an output schema present, the description need not explain return values, and safety behavior is covered by annotations; the added error taxonomy makes it complete enough for a one-parameter lookup tool. Only the missing when-to-use routing against sibling search/card tools keeps it from a 5.

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 single parameter (item_id_or_url) is already documented in the schema as a goods id or megamarket.ru URL. The description adds no syntax, format, or constraint detail beyond that, so 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 verb ('Fetch'), a specific resource ('Megamarket product card'), and scope ('one'), so an agent can tell it apart from megamarket_search. It does not, however, explicitly differentiate itself from the many sibling *_card tools beyond the marketplace name.

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?

The description gives no guidance on when to use this card lookup versus megamarket_search, compare_prices, or the other marketplace card tools. Usage context is implied only by the tool name.

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