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

Annotations already mark the tool as read-only, and the description adds useful behavioral context beyond that: 'If Vortex has no rule on file for the destination it says so instead of returning a confident guess.' The example also sets expectations about real-world totals. No contradiction with annotations.

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?

The description is efficient and well-structured, front-loading the core behavior, then providing a concrete example, then a 'When to use' section. The price line is relevant for cost-aware selection. Nothing is verbose, though the example plus pricing could be seen as slightly more than strictly necessary.

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?

Given there is no output schema, the description does a good job explaining what the result contains: itemized cost components and the name and effective date of the tax rule. It also covers the no-rule fallback. It does not deeply describe all input combinations, but the schema already covers those, so the description is reasonably complete.

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 schema already documents destination, product, item_usd, and shipping_usd. The description's example with a US$120 item into Brazil adds context but does not materially improve parameter semantics beyond what the schema provides. Baseline 3 is appropriate.

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 clearly identifies the tool's function through its output specification: item plus shipping, import tax, and local tax itemized for a destination, plus the tax rule applied. The example and 'shelf price is not the number to budget against' reinforce the landed-cost purpose. It does not explicitly name or differentiate among sibling tools, so it falls just short of a 5.

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?

The description gives explicit guidance: 'Call this before committing to a cross-border purchase, and before comparing two stores in different countries.' This provides clear context for when to use the tool. It does not mention alternative sibling tools or exclusions, which prevents a 5.

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