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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful behavioral detail beyond that, including the HTTP GET endpoint, the 20-item cap, and the optional response-field filter. It does not describe error cases or response shape, but it is reasonably transparent for a read-only lookup tool.

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 description is two concise sentences, front-loaded with the core purpose and followed by the key parameter guidance. Every clause adds value without 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?

For a read-only detail-by-ID tool, the description covers the endpoint, required parameter, limit, and optional field filter. It omits the `account` parameter and does not describe return structure, but the output schema is absent and the annotations cover the safety profile, so the description is adequate with minor gaps.

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%, so the description must compensate. It explains `ids` (list, max 20) and `attributes` (comma-separated fields), but it does not explain the optional `account` parameter, leaving one property undocumented and potentially confusing.

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?

The description clearly states what the tool does: it details one or more listings/ads by ID via GET /items?ids=. It explicitly uses 'por id' and names the resource, distinguishing it from sibling tools like mercadolivre_search_items or mercadolivre_list_items.

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 clear usage context: invoke when you have anúncio IDs, provide `ids` as a list with a max of 20, and optionally use `attributes` to filter fields. It does not explicitly name alternatives or say when not to use it, but the ID-based scope makes the use case evident.

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