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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds real context beyond that: the live proxy upstream (MDIC Comex Stat), the sort order (descending by USD FOB value), and that omitting both product params widens scope to all of Brazil's trade. It does not mention data freshness/latency or rate limits for the live proxy.

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?

Two sentences plus example phrasing, front-loaded with what the tool returns before the parameter rules. The inline examples in quotes partly duplicate the schema's own example block, which is the only real slack, but they double as usage guidance so they still earn their place.

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 no output schema, the description does the work of saying what comes back: partner countries ranked descending by USD FOB value, sourced live from Comex Stat. It stops short of describing record shape (country name, value, share, rank) or handling of empty/unknown NCM codes, which an agent would need for edge cases.

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%, so every parameter already carries its own explanation (8-digit NCM, 2-digit chapter, flow default, limit default and cap of 50). The description restates the either/or constraint and the omit-both case, which is useful but largely duplicative; the FOB sorting note is the only genuinely new semantic detail.

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 first clause states a specific verb+resource: top partner countries for a Brazilian product in a given year, with a named source (MDIC Comex Stat). It is distinguishable from siblings like br_trade_top_products and br_trade_flows by what it ranks, though it never names those siblings explicitly to lock in the contrast.

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?

It gives explicit invocation context with two worked natural-language examples tied to concrete parameter values, and states the mutually exclusive rule (ncm OR chapter, omit both for overall totals). It does not say when to prefer br_trade_flows or br_trade_top_products instead, so the alternative-selection guidance is incomplete.

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