get_shipment_label

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

With no annotations, the description carries the full burden and does so: it discloses the local-file write side effect, the returned path/size, both output formats, the state precondition, the failure modes for unsupported logistic types, and that Meli errors are surfaced as-is.

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?

Front-loads the action and return value, then packs preconditions and gotchas into a compact trailing block. Every sentence earns its place with no filler.

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?

No output schema exists, so the description must explain the return, and it does (absolute file path plus size in bytes). Combined with format options and failure behavior, an agent has everything needed to call and interpret the result.

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 coverage is 100% and the schema already documents both parameters, including the order.shipping.id origin and the pdf/zpl2 enum. The description largely restates that, adding no syntax or format detail beyond the structured fields, 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 (download/save) and resource (Mercado Envios shipping label) plus the concrete side effect (saved to a local file), which clearly separates it from the sibling get_shipment.

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?

Gives real preconditions and routing advice: label only exists after 'ready_to_ship', flex/self-service logistics have no printable label, and 'call get_orders first if you only have an order id.' It does not explicitly contrast with get_shipment, but the when-to-use context is strong.

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