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

Annotations already declare read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: which product categories the estimate is reliable for (electronics, consoles, phones, laptops, branded items named by model), which is a support boundary an agent needs. It does not say how the price is derived or what the response contains, but the annotation set lowers the bar.

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 sentences, front-loaded with the trigger condition, followed by scope limits and then exclusions with named alternatives. No filler and every sentence carries routing or scoping 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?

With only two parameters, full schema coverage and rich annotations, the main remaining gap is that there is no output schema and the description never indicates what comes back (a point estimate, a range, per-site pricing). The domain guidance compensates largely but not entirely for that absence.

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 baseline is 3. The description still adds real meaning for the `product` parameter by requiring model-level specificity ('branded items named by model', example 'PS5 Slim') and clarifying that vague or generic items are out of scope, which the schema's 'as specific as the person said it' only half states.

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 concrete verb and resource ('what a second-hand item sells or resells for on Vinted'), plus a secondary purpose (max buy price to resell at a profit), with a concrete example query. It explicitly names the sibling tools it is not and the situations they cover, so an agent can route 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?

Gives positive triggers (what a used item sells for, what it's worth used, max price to pay for resale profit), an explicit 'Do not use for' list (new retail prices, one specific listing link, what to list one's own item at), and names the correct alternative tools (check_listing_deal, suggest_listing_price) for two of those cases.

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