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

Annotations already declare readOnly, idempotent, and non-destructive behavior; the description adds substantive context: unit price depends on the style's total units, shipping assumptions, estimated-not-guaranteed delivery dates, sales tax calculated at checkout, and 'Creates nothing.' There is no contradiction with 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?

Front-loads the core purpose and output components, then branches on ship_to_zip, then notes tax and the no-write caveat. Dense but every sentence adds decision-relevant information with no repetition.

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?

No output schema exists, but the description enumerates the returned pricing fields and delivery-date behavior; annotations cover safety and the schema covers parameters. This is sufficient for an agent to call the tool and interpret its results 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?

Schema coverage is 100%, so the baseline is 3; the description adds meaningful semantics for ship_to_zip (ZIP-specific shipping and estimated delivery dates, contiguous-US default when omitted) and the pricing rule for items. It does not restate every schema constraint, such as 1–40 lines or qty maximum, but adds useful meaning beyond the schema.

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/resource: exact prices for SKUs and quantities, and enumerates the outputs (unit price, merchandise subtotal, shipping, total before tax). The phrases 'as the Standard Blanks cart would charge them' and 'Creates nothing' distinguish it from build_cart.

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 clear context for pricing and explains the ship_to_zip branch, including the contiguous-US fallback and that no delivery dates are given without it. It does not explicitly name build_cart as the alternative for actually creating a cart, so it lacks a full when/when-not routing statement.

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