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

Annotations already declare readOnly/openWorld/idempotent, so the safety profile is covered. The description adds genuinely useful operational context not in the schema: 15-minute result caching, the 1-request cost (including cache hits), and that failed searches are free. It does not reveal anything contradictory.

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?

Four short sentences, each carrying distinct information (scope, paging, caching, cost, docs link), with the core purpose front-loaded. No filler or repetition.

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?

For an 11-parameter, annotated read tool it covers paging, caching, cost, and links docs, which is strong. However, with no output schema, it never indicates what a sold listing row contains (sale price, sold date, condition), which is the point of a sold-listings tool, leaving a small completeness gap.

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 every parameter is already documented in the schema. The description only loosely reinforces keyword scope and the 100-row cap; it adds no new parameter semantics beyond what the schema provides, so 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 uses a specific verb and resource ('Search ... Mercari US sold listings by keyword') and bounds the scope ('one page ... up to 100 rows'). The 'sold' qualifier implicitly separates it from the sibling mercari_listings, but no sibling is actually named, so routing still requires inference.

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 tells the agent how paging works (cursor) and the cost model, which implies when the tool is worth using, but it never states when to choose this over mercari_listings or the other marketplace sold tools. Usage context is implied rather than explicit.

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