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

Annotations already mark readOnlyHint=true, and the description adds consistent behavioral context: live price/stock and delivery-reach filtering. It also discloses the per-call price. There is no contradiction with the annotations, and no hidden mutation or side effect is suggested.

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 core behavior is front-loaded in the first sentence, followed by a sharp when-to-use rationale and cost. There is no filler, no restatement of parameter names, and every sentence contributes to correct tool selection and invocation.

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 read-only search tool with 100% schema coverage, the description covers what the result contains (reachable storefronts with live price and stock), when to call it, and its cost. It could specify the return shape in more detail since there is no output schema, but nothing essential for invoking 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?

Schema description coverage is 100%, so the baseline is 3: the schema already documents need, destination, limit, in_stock_only, and max_price_usd. The tool description only restates the destination/reach concept without adding meaningful detail beyond the schema.

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 opens with a specific verb and resource: 'Search real storefronts for a product' and immediately clarifies the tool's differentiator—returning only items that can ship to the destination. This clearly distinguishes it from generic product indexes and gives an agent a precise mental model.

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 when-to-use guidance: 'Call this before shopping anywhere else' and explains why, citing country-specific storefronts and late-stage checkout failures. It does not name concrete sibling tools or provide when-not-to-use conditions, so it stops short of a 5.

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