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

Annotations already flag a non-idempotent, non-destructive write, so the bar is lower; the description still adds the concrete capacity ceilings that annotations cannot express. It does not say what happens when a cap is exceeded (error vs. partial add), which is the one behavioral gap.

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?

Two short sentences with zero filler: the action and the id provenance come first, then the hard caps. Everything stated is actionable.

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 three-parameter mutation with a well-described schema, the description covers action, valid id sources and limits. The missing piece is failure behavior on cap violation and confirmation of what the response contains, though the currency field already notes the XOF price is always returned.

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 67% and the schema already documents cart_id, currency and quantity bounds in detail. The description still adds meaning beyond the schema by declaring the cart-level limit of 20 distinct books and by pinning the id source, which the nested items.id field leaves unqualified.

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 pairs a specific verb ('Ajoute') with a precise resource ('un ou plusieurs livres ... au panier') and even names the sibling tools that produce valid inputs (search_books, get_book). This makes it distinguishable from create_cart, which provisions the cart rather than filling it.

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 tells the agent what inputs to use (book ids from search_books/get_book) and states the operating envelope: 20 distinct books, 10 copies per book. It stops short of naming alternatives or exclusions (e.g., that remove_from_cart handles reductions, or that create_cart must run first), so usage is strongly implied rather than fully enumerated.

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