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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds genuinely new behavioral facts beyond that: quoting does not reserve anything, unavailable placements are refused rather than partially quoted, and niche items are priced at the outlet's niche price with no shareUrl returned when it diverges from standard pricing. These are non-obvious consequences an agent could not infer from 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?

Four sentences, front-loaded with the core purpose and fee, followed by usage then edge-case behavior. Every sentence is load-bearing, though the final niche/shareUrl sentence is dense and could be tightened slightly.

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?

With no output schema, the description carries the return-value burden and does mention shareUrl implicitly, but it does not describe the overall shape of the priced response (totals, per-item breakdown, fee line). Given the tool's simplicity and full schema coverage, this is nearly complete but leaves a small gap around what the quote returns.

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 100% with a single nested 'items' parameter, so the baseline would be 3. The description goes beyond the schema by explaining the pricing consequence of the niche field (outlet niche price, refusal where unsupported, absence of shareUrl), which adds real semantic meaning to how 'niche' affects the call.

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 states a specific verb and resource ('Price a set of placements exactly as the store's checkout would, including the 3.5% processing fee') and clearly differentiates itself from the order-creating siblings by framing itself as the pre-order pricing step. An agent can tell this apart from create_order, plan_placements, and compare_placements without opening any schema.

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?

'Use this to give a client a total before creating an order' gives clear situational context and implicitly routes to create_order as the follow-up. It lacks an explicit negative case or named alternative for when NOT to quote (e.g., when availability is unknown), so it falls just short of the top band.

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