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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, but the description adds crucial context: the 501 not_enabled response is expected until the limited-release API is enabled, and this is honest behavior rather than a bug. This goes well beyond the structured 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?

The description is three compact sentences with the purpose front-loaded in the first phrase. The second sentence explains the prerequisite, and the third sets failure expectations. There is no filler or repetition of schema/annotation details.

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?

The description covers purpose, prerequisite, and failure behavior, which is strong given the annotations and simple schema. It does not describe the successful return format, but for a gated tool that may always return 501, this is less critical. Overall, it is nearly complete for the tool's complexity.

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?

The input schema already fully describes q as 'Keyword query,' with 100% schema description coverage. The description does not add additional parameter-level detail, but given the schema's completeness, none is necessary. The tool-level context about sold items is useful but not parameter-specific.

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 opens with 'Sold/completed-item price comps,' which is a specific verb+resource statement that clearly identifies this as a search for sold eBay listings. This distinguishes it from sibling tools like search_ebay and the various get_* 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?

The description provides explicit context about the prerequisite: it needs eBay's Marketplace Insights API, which requires a separate limited-release approval. It also clearly states that until enabled, the tool always returns a 501 gate, which tells the agent when to expect failure. However, it does not explicitly name an alternative tool for active listings.

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