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

Annotations already declare readOnlyHint, idempotentHint true and destructiveHint false, so safety is covered. The description usefully reinforces that no order is placed, but says nothing about whether revalidation has hidden side effects (inventory hold, cart lock) or any auth/rate-limit requirements, so it adds modest value over the 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?

One sentence, zero filler, with the computed fields listed first and the critical non-mutating constraint front-loaded at the end of the same sentence.

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?

An output schema exists, so return values need no explanation, and the annotations cover the safety profile. The description is complete enough to call the tool, with the only residual gap being optional-parameter behavior for the four nullable inputs.

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% across 4 params, so the description must compensate; it does so only coarsely, mapping 'discounts' to coupon_code, 'points' to points_to_redeem, and 'addresses' to the two address strings. It never states that all inputs are optional or what happens when one is omitted, leaving real format/semantics gaps.

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 gives a specific verb ('revalidate') plus an enumerated resource set (cart, discounts, points, addresses, checkout total), which tells the agent exactly what is recomputed. The trailing clause 'without placing an order' separates it from the mutating sibling start_checkout, so no schema opening is needed to disambiguate.

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?

Usage is only implied via 'without placing an order', which hints at a pre-purchase preview scenario, but no sibling (start_checkout, validate_coupon, get_cart) is named as an alternative and no prerequisites or exclusions are stated. An agent must infer the correct moment to call it.

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