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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), but the description adds behavior those flags cannot express: results are limited to listings currently buyable or biddable, and not_found means sold/expired/withdrawn rather than non-existent. That freshness constraint and error semantics materially change how an agent should interpret results.

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?

Four sentences, none of them filler, and the most important content (what comes back, where the id comes from) is front-loaded. It is denser than needed in the field enumeration, which partially duplicates the output schema, but it remains readable and purposeful.

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?

Given two optional identifier params, a rich output schema, and annotations covering the safety profile, the description supplies exactly the missing pieces: value provenance, freshness of results, and recovery on not_found. An agent has everything needed to select and call this tool correctly.

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 0% and neither id nor slug is documented in the schema, so the description carries the burden. It does this well by naming the source of the values (from search_catalog) and treating id and slug as interchangeable identifiers, but it does not state that both are optional, that they are mutually exclusive, or what happens if both are supplied.

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+resource ('Get the full public details of one listing') and enumerates the returned fields (description, price in EUR, condition, brand/designer, dimensions, materials, photos, seller, link). It is clearly distinguishable from search_catalog (broad listing retrieval) and similar_items (comparable pieces), so an agent can route correctly without opening sibling schemas.

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?

Explicitly says to pass the id/slug originating from search_catalog and to check an item here before recommending a specific piece, which is direct when-to-use guidance. It also handles the failure branch by naming alternatives (search_catalog, similar_items on a comparable listing) rather than leaving the agent to guess.

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