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

Annotations already mark readOnly and openWorld. The description adds valuable context beyond annotations: it discloses the data source (homepage SEO metadata), that codes are unverified, and explicitly names unavailable channels. The per-result pricing is also stated, which is useful behavioral information.

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?

Three compact sentences, front-loaded with the action and scope, then constraints, then pricing. No waste.

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 an output schema present, return details needn't be repeated. The description covers source, limitations, pricing, and safety context well. The only gap is the undocumented 'product_category' parameter.

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 50%; the 'domain' parameter is documented in the schema, but 'product_category' has no description anywhere. The description does not compensate for this gap or add meaning 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?

States a specific verb (extract) and resource (explicit coupon candidates from merchant homepage SEO metadata), which is clear. The 'checkout' context and mention of unavailable ad channels help distinguish it, though sibling differentiation could be sharper.

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?

Explicitly says to use it 'during checkout' and clarifies what it does not claim (a code works at checkout) and what sources are unavailable. No direct naming of alternatives, but the scoping is clear.

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