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

Annotations only cover read-only/idempotent/non-destructive safety; the description adds substantial semantic context beyond that: what is bundled into the quote (shipping tier, promotion, duties for US), the 219-country coverage, and the country-specific extra fields (`local`, `storeUrl`, localised item URLs). This is exactly the value-add the annotations cannot supply.

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 lead sentence is well front-loaded, but the middle clause listing 24 country codes followed by "and 174 more countries worldwide" is self-defeating bulk that could be compressed. The final sentence about local currency and store URLs is long but does carry real information.

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 takes on the burden of describing return values and does so explicitly (checkoutUrl, `local` amounts, `storeUrl`, localised item URLs). For a 2-parameter read-only tool with annotations already covering safety, nothing material 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?

Schema coverage is 100%, so the baseline is 3; the description earns extra by explaining quantity-through-repetition of SKUs and by spelling out country-driven behaviour (US duty inclusion, per-country currency and store URL) that the bare `country` parameter does not convey. Minor deduction for the sprawling country enumeration, which adds bulk more than precision.

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?

Opens with the exact question the tool answers ("what does this cost in total, delivered?") and then enumerates the return payload — items, checkout shipping tier, promotion, EUR total. A specific verb-plus-resource framing that is clearly distinct from search_products, get_product and store_info.

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 "what does this cost in total, delivered?" framing makes the when-to-use case obvious, and "Pass the same SKU twice for quantity 2" tells the agent how to express quantity. It stops short of naming an alternative sibling or an explicit when-not condition, so it is not a full 5.

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