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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely useful context beyond them: prices are in USD, include printing plus USPS First-Class postage, and apply to US addresses only — a real constraint on interpretation of results. It stops short of noting whether prices are quantity-dependent or how current they are.

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 parenthetical sentence with zero waste; the core action leads and the qualifiers follow. Every clause (currency, inclusions, geography) earns its place by preventing misreading of the returned prices.

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 zero-parameter, read-only catalog tool with no output schema, the description conveys what is returned (mail products and prices) and the conditions those prices assume. Minor gaps remain — no mention of price granularity or freshness — but nothing essential to calling it correctly is missing.

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 tool takes zero parameters, so the schema carries no semantics to supplement and the baseline of 4 applies. The description correctly avoids inventing parameter detail and instead spends its words on output meaning and constraints.

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 and resource ('List mail products and prices') plus scoping qualifiers (USD, printing + postage included, US addresses only). The function is unambiguously distinct from the order/creation siblings, which all act on existing or new orders rather than a catalog.

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: an agent can infer this is the catalog/pricing lookup to consult before create_letter, create_postcard or pay_order, but no when-to-use statement or alternative is named. There is no explicit guidance on when pricing data is needed versus when get_order already suffices.

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