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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond that: the US marketplace scope, the shape of each hit, and the item_id chaining to ebay_get_item. It does not mention pagination or rate limits, which are minor given the low bar set by 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?

Three short sentences, front-loaded with purpose, then return shape, then the routing hint. Every sentence earns its place with no 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 an output schema present and 100% schema coverage, the description need not explain return values, yet it usefully summarizes them and adds the marketplace scope and follow-up path. It is essentially complete; the only missing nuance is pagination/limit guidance, which the schema already covers.

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 all six parameters (q, sort, limit, filter, offset, category_id) are already documented in the schema, including the filter syntax and category lookup pointer. The description adds no parameter-level meaning of its own, so the baseline 3 is appropriate.

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 (Search) and resource (active eBay listings) and narrows the scope to the US marketplace. It also distinguishes itself from ebay_get_item by positioning search as the discovery step and get_item as the detail step, so an agent can route correctly without opening either 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?

It gives clear follow-up guidance: use ebay_get_item with the returned item_id for full detail, which establishes the search-then-fetch workflow. It stops short of stating when not to use this tool or naming alternative search paths (e.g., category scoping via ebay_get_categories), so it is clear context without explicit exclusions.

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