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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered externally. The description does add two genuinely useful traits beyond the annotations: a cost of 2 credits and the fact that some outputs are gated behind paid plans. Against that, it claims 'each month comes with the previous month's balance' while the schema makes that balance conditional on the `changes` flag, which is a small internal inconsistency that could mislead an agent about the default payload.

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, front-loaded with the data scope and followed by the payload/extras and cost. Every clause carries information, and the parenthetical credit cost is compact. A slightly crisper split between what free data contains and what requires a paid plan would improve it.

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 an output schema present, annotations declaring it a safe read, and full schema coverage, the description only needs to convey scope, extras, and cost, and it does all three. The remaining gap is the ambiguity over free-versus-paid output content, which is exactly the detail an agent would need to explain results to a user.

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 the baseline is 3 because the schema already documents all three parameters. The description still earns credit by tying the richer outputs (MoM/YoY changes, rolling 12-month totals, last 12 months) to paid plans, which is plan-tier context the schema does not supply. It loses a point for the conflict noted above about whether the previous month's balance is always included.

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 names a specific verb and resource: monthly US international trade data covering exports, imports, and the goods-and-services balance on a BoP basis. That is far more precise than the bare name 'TradeBalance'. It does not, however, contrast itself with the many other economic-data siblings (GDPData, CPIInflation, BalanceSheet), so an agent must infer that this tool covers trade flows and not corporate or fiscal balances.

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?

Usage is only implied: the mention of historical months and the 'paid plans' extras hints at when the optional flags matter, but the description never says when to pick this tool over a related economic indicator or what happens on free plans. There are no explicit when-to-use or when-not-to-use statements.

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