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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and non-openWorld, so the safety profile is covered. The description adds genuinely useful context beyond that: payments are handled externally via Stripe/Mobile Money links on an external page and the author pays themselves, meaning the tool never initiates a transaction.

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 content is front-loaded with the offer name and what it contains, and the payment constraint is stated last. It is dense with useful detail, though the full bilingual duplication roughly doubles the length for the same 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?

For a zero-required-parameter, read-only informational tool with no output schema, the description tells the agent what data it will get back (plans, prices, lead times, inclusions, payment links) and where payment happens. Little else is needed for correct invocation.

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% and both parameters (lang, site) are fully documented there with enums and defaults, so the description adds nothing about them. Baseline 3 applies when the schema does the heavy lifting.

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 (author website offer) and enumerates what it returns: plans, prices in three currencies, lead times, inclusions and payment links. This clearly separates it from transactional siblings like create_cart or start_checkout, but it never names the closest sibling (get_isbn_offer) as a distinct alternative.

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?

Usage is only implied: the agent can infer this is the lookup tool for author-website offer questions. There is no explicit when-to-use statement and no mention of how it relates to siblings such as get_isbn_offer or start_checkout, so the agent must infer the routing.

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