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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond those: privacy limits ('no seller names or thumbnails') and a billing rule ('a search with no results is not charged'), which are genuinely useful for an agent deciding to call it.

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?

Purpose is front-loaded in the opening clause, and the field list, marketplace scope and billing note all earn their place. It is dense with colons and semicolons but not padded with filler.

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 compensates by listing the returned fields, and it covers scope, privacy and billing. Minor gaps remain (no pagination behavior beyond the limit param), but for a read-only search tool it is essentially complete.

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%, so the schema already documents all five parameters fully. The description's mention of 'Eight eBay marketplaces, last 1 to 90 days, new or used' merely restates the site, days and condition constraints already in the schema, adding little new meaning. Baseline 3 applies.

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 and resource: 'send a keyword, get sold items as JSON for resale comps.' It also enumerates the returned fields (sold price, currency, shipping, total, sale date, condition, listing type, bids, seller feedback), so an agent knows exactly what it produces. The eBay-sold scope cleanly separates it from the sibling 'amazon' and other listing tools.

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?

'for resale comps' implies the intended use case, giving some context on when to reach for it. However, it never names an alternative or states when NOT to use it versus comparable siblings like 'amazon' or 'shopify-products.' Usage is implied rather than explicitly guided.

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