Calculate and reserve one coupon

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

Annotations declare a non-destructive, non-idempotent, open-world write; the description adds the crucial nuance that the write is a 'temporary quote reservation' and that totals are 'authoritative' (server-computed, not client-supplied). It does not disclose the reservation's lifetime/expiry or what a repeated call does given idempotentHint=false, which are real gaps for a write tool.

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?

Three short sentences with the action front-loaded, followed by usage and exclusion. Nothing is redundant and every clause carries information.

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?

Adequate at the workflow level, but for a nested-object, three-parameter, non-idempotent pricing/reservation tool with no output schema, an agent still lacks guidance on reservation expiry, error cases for invalid codes, and how the many optional context fields affect results.

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 only 33% and the description compensates minimally, only implying that context.cart is the cart being priced. The optional context fields that plausibly change eligibility or totals (user age/sex, location, shipping amount, payment_method, attributes, unit_id, brand_id) are explained nowhere in schema or description, and cart_id vs the inline cart array is never clarified.

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?

Specific verbs (validate, calculate, create a reservation) applied to a single named resource (one coupon code against the cart). The closing clause 'Do not use for catalog discovery' actively separates it from find_eligible_coupons/recommend_integration_flow, and 'single' plus the sibling quote_multiple_coupons makes the scope 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?

Gives an explicit when-to-use ('before redeeming or displaying a final discount') and one explicit exclusion (catalog discovery). It stops short of naming the alternative tools directly or stating what to do if the coupon is invalid, so it is clear but not fully routing.

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