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

Annotations already indicate a non-read-only mutation, and the description adds useful behavioral context: it return a C01-style id, requires whole-gram weights and whole-centimetre dimensions, and explains that dimensions enable chargeable weight. No contradiction exists with the annotations.

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 sentences with no filler: the first states the action and return values, the second gives a meaningful rationale for the optional dimensions. The structure is front-loaded and every phrase earns its place.

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?

The description covers the action, the return value, and the semantic importance of dimensions. Although there is no output schema, the description gives enough about the C01-style id and fields an agent can expect; remaining details are already carried by the input schema.

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 86%, so the baseline is 3. The description adds value beyond the schema by emphasizing WHOLE units and by explaining why the optional dimensions matter ('Dimensions are what make a chargeable weight possible'), helping the agent decide whether to supply them.

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 uses a specific verb and resource: 'Add a carton to a packing list', and clarifies that it returns a C01-style id plus dimension and weight fields. This clearly distinguishes it from siblings like pack_item or packing_list_create.

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 implies use when a carton must be added to a packing list, but gives no explicit when-to-use or when-not-to-use guidance and does not mention any alternative sibling tools. An agent must infer the appropriate context from the tool name and basic action.

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