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

Annotations only declare readOnlyHint and openWorldHint=false, so this is a safe local computation. The description adds real context beyond annotations: the estimate uses 'official rules in force today' (time-sensitivity) and the tariff code is auto-suggested from the plain-word product description rather than required. No auth, rate-limit, or error behavior is described.

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 cost scope in the first sentence, then the input guidance, then a concrete example. Three sentences with essentially no waste, though the example could arguably be folded in.

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 10-parameter read-only calculator with no output schema, the description conveys what is computed, the rules basis, and the key input convention. It does not explain what the returned estimate looks like (only a number? a breakdown?), which is the main residual gap given no output schema.

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 high (90%), so the baseline is 3, but the description adds meaning beyond it by clarifying the relationship between 'product' (plain words) and 'tariffCode' (optional, only if known, otherwise suggested) and by hinting the product description drives the code lookup.

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 (estimate) and resource (door/landed cost for one parcel) with explicit scope: CA-US cross-border, covering duty, tariffs, surtaxes, sales tax and carrier fees. An agent can distinguish this from border_rules_status or border_lane_insights without opening the schema.

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 a concrete when-to-use cue via the shopper example ("what will I pay on a hoodie from a US store shipped to Ontario?") and instructs 'describe the product in plain words'. It does not explicitly name sibling tools or exclusions, so routing versus border_quote is left to inference.

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