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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the description does not need to restate non-mutation. It adds useful context about the authorized cart, but it does not disclose behaviors such as how invalid/expired coupons are handled or what the validation result contains.

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?

A single, front-loaded sentence with no filler. Every word contributes meaning, and the description is appropriately sized for a simple single-parameter tool.

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 low-complexity, read-only tool with an output schema and only one parameter, the description plus annotations cover most operational needs. The main gap is the lack of explicit usage guidance, but the authorized-cart context and input schema make it usable.

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 0%, and the description does not explicitly explain the 'code' parameter beyond inferring it is the coupon code from the tool name. The parameter name and length constraints are minimally self-explanatory, but the description adds no real semantic detail.

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 ('validate') and a clear resource ('coupon') with the scope 'against the authorized customer cart.' It distinguishes validation from other cart operations, though it does not explicitly differentiate from a coupon-specific sibling because none exists.

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 phrase 'against the authorized customer cart' implies the tool is used in a cart/checkout context, but there is no explicit statement of when to use it or when to prefer an alternative. Since no sibling coupon tool exists, the ambiguity is low.

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