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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds that it returns an estimated cost range and lead time, but says nothing about accuracy caveats, carrier coverage, or rate limits beyond what is implied by 'Estimate'.

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?

Five short, front-loaded sentences that cover purpose, use case, inputs, and output with no padding. The choppy fragment style is efficient, though not elegant.

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?

An output schema exists so return values need not be explained, and the estimate semantics are clear. But the description omits the zone-based input model entirely and substitutes a country-to-country model that the tool does not support, leaving the agent with an inaccurate mental model of the call.

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 100%, so the baseline would be 3, but the description actively misstates the parameters: it lists 'from-country, to-country' and 'by carrier' when the schema only accepts a single from_zone enum (destination zone), weight_kg, and dimensions_cm. An agent trusting the description could look for parameters that do not exist.

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 states a specific verb and resource ('Estimate international shipping cost and delivery time') and scopes it by carrier and weight, which distinguishes it from siblings like calculate_shipping_volumetric and calculate_delivery_cost. However, its claim of the input shape ('from-country, to-country') does not match the actual schema, which slightly muddies an otherwise clear purpose.

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?

'Use for e-commerce or expat shipping' gives a use case but no when-not guidance and no explicit alternatives. The pointer to list_bundles for related 'voyage' calculators is a helpful routing hint, though it is a bundle-listing tool rather than a directly competing calculator.

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