Update Item

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

With no annotations, the description carries the burden and it discloses key behavior: only supplied fields are changed, and site_id must match the owning country profile or the write is rejected with 403. It does not cover every side effect, but the critical failure mode and patch semantics are explicitly stated.

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 compact, front-loaded with the operation, and uses a bolded warning plus two minimal examples. Every sentence contributes operational 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 write operation with no annotations and a nested input object, the description addresses the most likely failure (site_id ownership) and partial-update behavior. Since an output schema exists, the lack of return-value detail is acceptable, though the description could mention item-not-found behavior.

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?

The description adds concrete usage meaning for site_id, price, and stock through examples and the ownership rule, but context indicates 0% schema description coverage. It does not compensate for all nested fields, leaving most field semantics to the schema's property descriptions.

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 states a specific action ('Update an existing MercadoLibre listing') and immediately clarifies partial-update semantics ('Only provided fields are changed'). This differentiates it from create_item, delete_item, and relist_item even without naming them.

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?

Using the word 'existing' establishes when the tool applies, and the two usage examples show concrete invocation patterns for price and stock updates. It does not explicitly list alternative tools or when-not-to conditions, but the context is clear enough for selection among the update/create/delete siblings.

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