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

Adds genuinely non-obvious behavior: the call is a no-op preview that returns a change summary plus a confirmation link, and only the merchant on that page can complete it. That is real context beyond the annotations. It sits in mild tension with readOnlyHint=false, but the semantics (it stages rather than performs) make that a nuance rather than a contradiction. It does not state what the preview contains or that a tracking number eventually results.

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?

Front-loaded with the action, then the critical caveat about no immediate change. Three tight sentences. The money-units sentence is generic boilerplate irrelevant to a one-parameter shipping tool and is the one line that does not earn 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?

For a single-parameter tool with no output schema and annotations covering safety, the description supplies exactly the missing piece: the two-step, merchant-confirmed execution model. Nothing an agent needs in order to invoke it correctly is absent, and return-value detail is unnecessary since the call yields only a preview.

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?

Only one parameter (orderNumber) and schema description coverage is 100%, so the schema fully documents it, including the 'human order number, e.g. 1003' format. The description adds nothing about the parameter. Baseline 3 applies. The 'integer minor units (cents)' sentence concerns money, which this tool does not take, so it does not help parameter understanding.

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 specific verb and resource: 'Book an order's parcel with the shop's carrier.' An agent immediately knows this is a shipping/label action on a single order. It does not explicitly distinguish itself from nearby siblings like orders_update_shipment, orders_fulfil, or orders_remove_shipment, so it falls short of a 5.

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 establishes the workflow context (preview then merchant confirms on a page) but never says when to pick this over orders_fulfil or orders_update_shipment. The most useful routing hint — 'for orders auto-booking missed or failed' — lives only in the schema description, not here.

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