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

Annotations already declare readOnly, idempotent, non-destructive, open-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: it explains the delivered-price basis, the sold-median comparison, the verdict categories, and that cheaper listings are restricted to ones shipping to the buyer. No latency, rate-limit, or failure-mode notes keep it from a 5.

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: the core action comes first, then the output shape, then the secondary feature (cheaper listings). Parenthetical detail carries the verdict vocabulary without a second sentence of waste.

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 an output schema and rich annotations, the description only needs to frame intent and it does so fully, including the shipping constraint that shapes results. It omits edge-case behavior (ended/invalid listings, unsupported domains), though the schema enumerates supported marketplaces, which mitigates this.

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, but the description adds meaning by framing the comparison as a *delivered* price, which justifies the country parameter's shipping role beyond the schema's own wording. Both parameters are already well documented in the schema, so the added value is modest rather than decisive.

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 and resource ('Judge whether an eBay listing is a good price') and enumerates the exact outputs (great / fair / above typical / overpriced, % vs sold median, cheaper shipping alternatives). This is clearly distinguishable from get_used_price (model-level pricing) and list_tracked_models 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?

The context of use is clear: the agent has a specific listing (schema says 'the eBay listing link the user pasted') and wants a price verdict, not a general model price. It does not explicitly name get_used_price as the alternative for model-level pricing or state exclusions, so it falls short of a 5.

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