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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses the critical caveat that codes are not verified at checkout, identifies the data source as homepage metadata, and states the pricing model of $0.01 per non-empty result. It also clarifies what the tool will not do (apply coupons or place an order), which is exactly the kind of behavioral context an agent needs before calling it.

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 four tight sentences with no wasted language. Critical caveats (unverified codes, pricing) and routing guidance are front-loaded and easy to scan.

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 the output schema exists, the description need not explain return values. It still covers the essential context: source of the codes, lack of checkout verification, cost per non-empty result, intended usage, alternative tool, and explicit non-actions.

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 domain, context, and product_category parameters are already well documented in the schema. The description adds general context about the domain being a shop's homepage metadata, but does not add parameter-specific syntax or constraints beyond what the schema provides.

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 names a specific resource (coupon code candidates), a specific source (homepage metadata of a shop), and the accompanying source text. It also explicitly distinguishes the tool from adjacent capabilities by saying it does not apply coupons or place an order and by pointing to universal_product_url_to_json for product prices and availability.

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?

It gives a clear use case (collect possible discounts before checkout), names the alternative tool for product prices and availability, and states the key exclusion (does not apply coupons or place an order). It also warns that codes are not verified at checkout, which directly shapes when the result should be trusted.

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