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

Adds substantial context beyond the annotations: the tool renders an interactive widget where the user picks address and payment as tappable options, those are chosen in the widget rather than in chat, and it requires sign-in and a non-empty cart. This is exactly the behavioral guidance the readOnly/openWorld hints don't convey.

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 front-loaded sentences with no filler; the pricing scope, widget behavior, prerequisites, and 'no order placed' caveat all earn their 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?

With annotations covering safety and an output schema covering return values, the description fills the remaining gaps: the in-widget selection model, sign-in and non-empty-cart prerequisites, and explicit non-placement of orders.

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 already 100%, so baseline is 3. The description adds meaning by explaining that address and payment are selected by the user in the widget rather than passed in chat, clarifying the role of the optional addressId/paymentTypeId.

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 (prices the current cart for checkout), enumerates the price components, and clarifies it also renders an interactive selection widget. The clause 'Places no order' cleanly distinguishes it 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?

'Use when the user is ready to check out' gives a clear trigger, and the prerequisites (sign-in, non-empty cart) are stated. It stops short of naming place_order as the next step, but 'Places no order' implicitly routes the agent away from it.

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