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

Annotations already declare readOnlyHint=true, and the description reinforces that with 'Read-only preview itself,' while adding a critical behavioral fact: the preview includes a confirm button that triggers register_sale, meaning the actual sale mutation happens later. It also discloses that the preview resolves product names, unit prices, and totals, providing context not captured by 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 focused sentences pack in the purpose, key features, and safety note without redundancy. The information is front-loaded with the primary action and specifics follow logically, making it easy to parse.

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 tool is simple with two params, complete schema explanations, and a clear behavioral description. The description explains what the preview shows and the confirm action, and with no output schema, nothing else is needed for an agent to invoke it correctly.

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 input schema covers all parameters with descriptions (100% coverage), so the baseline is 3. The description adds value by indicating that the preview resolves product names, unit prices, and totals, implying the caller only needs to supply productId and quantity without manually computing prices. This clarifies the intended semantics of the items parameter.

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 clearly states the tool opens a visual preview of a cash sale with resolved details and a confirm button, distinguishing it from other 'open_*' UI tools such as open_cobro_status or open_pending_orders. The verb 'opens' and the preview/confirm behavior make it specific and unambiguous.

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 the tool is used to preview a sale and obtain user confirmation before register_sale fires, giving clear contextual usage. However, it does not explicitly compare against alternatives or state when not to use it (e.g., when direct registration is desired), so it lacks exclusion guidance.

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