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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely new context the annotations lack: an entitlement gate ('Professional plan and above') and the fact that values are normalized to USD with spreads measured against a reference region. It omits rate limits or result-size behavior, hence 4 rather than 5.

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?

A single dense sentence with the core operation front-loaded and no filler; the em-dash example ('PP in Europe, US, China and the Middle East') earns its place by making the scope concrete. Slightly compressed punctuation makes it marginally less scannable than ideal.

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 carries the return burden and does communicate the shape of the result (USD prices plus spreads vs a reference). For a 5-parameter, zero-required read-only tool it covers purpose, key parameters and the plan gate adequately, though it never mentions the 10-code cap or the default European reference that the schema hints at.

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. The description still adds meaning beyond the schema by tying freight_per_unit and duty_pct together into a 'landed costs' outcome and clarifying that spreads are relative to the reference region, which explains why reference and duty_pct interact.

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 — comparing one material's price across named regions in USD with spreads against a reference region — and extends it to landed-cost comparison. An agent can distinguish it from price-listing siblings like get_prices or get_live_index. It stops short of explicitly naming which sibling to use instead, which keeps it at 4.

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 implies when the extra parameters matter ('add freight per unit and duty % to compare landed costs') and states a plan prerequisite ('Professional plan and above'), but never says when to choose this tool over alternatives such as get_prices or packindex_query. Usage is implied rather than spelled out.

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