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

The annotations already cover readOnly, idempotent, non-destructive and openWorld, so the safety profile is settled, and the description adds the content contract: what a response actually contains (presentation, themes, formats, price, page count, purchase and extract links). The explicit 'Pas de texte intégral' exclusion is real behavioural disclosure, because it stops an agent from treating this as a content-retrieval tool. It omits pagination or any state about the call itself, which caps the score at 4.

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 whole definition is one front-loaded sentence introduced by a clear label, with no filler. It is dense, with a nested parenthesis enumerating formats and price details, but everything listed earns its place because there is no output schema to carry the return shape.

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 two-parameter, read-only lookup with no output schema, the description adequately covers the return shape: themes, available formats, reference price in euros, page count, purchase and extract links. The one real gap is how the required slug is obtained. Annotations already cover the safety profile, so that gap does not sink overall completeness.

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 only 50%, and the parameter that the schema does not document is the required one, 'slug': nothing in the schema or the description says what a slug is or where to find it. The description mentions no parameter at all, though it does imply that the returned fare includes a page link. With the required identifier undocumented in both places, the description does not compensate for the coverage gap.

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 (a book fact sheet) and enumerates its parts: presentation, themes, commercial offer (formats, reference price in euros and page count), a link to the purchase page, and a link to the free extract. It is unmistakably a detail/fetch tool rather than the list/search tool. However, it does not name the sibling it differs from; an agent still has to infer that search_books supplies the slug.

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 closing note 'Pas de texte intégral' effectively tells the agent when not to call the tool if it needs the full text, which is useful. But there is no positive context for when to use it (e.g. 'call once you have a slug from search_books') and no named alternative for full-text needs. Usage is only implied by the shape of the description.

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