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

readOnlyHint=true matches the 'preview' framing, so no contradiction. The description adds value beyond the annotation by disclosing the payload the agent will receive and by establishing a mandatory call-order dependency on place_order; it does not discuss pricing volatility, error cases, or whether the preview reserves stock.

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, front-loaded with the action and its output inventory, followed by the imperative sequencing rule. No filler, no restating of the tool name.

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?

With no output schema and a single optional parameter, the description carries the burden well by listing what the preview surfaces. The remaining gap is the meaning and default behavior of delivery_address_id, which neither schema nor description resolves.

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?

There is one parameter with 0% schema description coverage, and the description never explicitly names delivery_address_id as an input or explains what omitting it does. The phrase 'delivery address' appears only as previewed content, so the agent must infer that address selection is a parameter rather than a fixed default.

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 ('Preview the order') and enumerates the preview contents (final items, totals with VAT and transport, delivery address, payment/delivery methods), so an agent knows exactly what this returns and how it differs from place_order.

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?

Gives an explicit sequencing rule ('Always call this before place_order'), which is strong when-to-use guidance naming the relevant sibling. It stops short of a when-not clause (e.g., browsing cart contents without intent to order), so it is clear but not complete.

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