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

Beyond the annotations (which only tell the agent this is a non-idempotent, non-destructive write), it discloses the anonymity of the cart, a concrete rate limit (10 per hour) and hard quotas (20 distinct books, 10 copies per book). It also discloses the return value cart_id, which matters because there is no output schema.

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 short sentences, front-loaded with purpose, then return contract, then limits. Every sentence carries distinct information with no padding or repetition.

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 one-parameter creation tool with no output schema, the description covers purpose, the return contract, rate limits and quotas — everything needed to call it correctly. Minor omissions such as cart lifetime/expiry or authentication expectations keep it from being fully complete.

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?

The single 'site' parameter is fully documented in the schema (100% coverage, enum with default and catalogue sizes). The description's restatement of the fr/en domain mapping adds nothing beyond that, so the baseline of 3 for high schema coverage applies.

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 concrete verb and resource ('Crée un panier anonyme') plus the two storefronts it applies to, which immediately distinguishes it from read-oriented siblings like get_cart. The scope ('anonyme', site fr/en) is specific enough that an agent can select it without opening the schema.

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 description routes the agent forward by explaining the returned cart_id is meant to be reused 'dans les autres outils du panier', which clarifies its position as the entry point of the cart flow. It stops short of explicit when-not conditions (e.g. what to do if a cart already exists) and names no sibling as an alternative, so it is clear context rather than full routing guidance.

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