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

No annotations are provided, so the description carries the full burden. It usefully discloses the return shape (id, URL, name, price in JPY, status, thumbnail, photo) and the billing behavior ('1 point per returned record'), which is genuinely valuable. However, it omits pagination behavior, authorization requirements, and rate limits for a 9-parameter search endpoint.

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?

Two sentences, zero filler, front-loaded with purpose followed by return fields and cost. Nothing is repeated from the schema and every clause earns its place.

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 a 9-parameter tool with no output schema and no annotations, the description does meaningful work by naming the returned fields and the per-record cost. Gaps remain around pagination semantics (start_page interaction with max_items) and auth, but an agent has enough to call it correctly.

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 every parameter, including enum meanings for sort/order/status and the price/JPY units. The description only restates the filter categories at a high level and adds no syntax or format detail. Baseline 3 applies when the schema does the heavy lifting.

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) plus resource (Mercari Japan items) and the filterable dimensions (keyword, category, sort, status, price). It does not explicitly distinguish itself from the sibling run_mercari_items, so an agent must infer that search vs. single-item lookup is the dividing line, but the purpose itself is unambiguous.

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 implies usage via the keyword-driven search framing and enumerates available filters, but gives no explicit when-to-use guidance, no exclusions, and no routing to alternatives such as run_mercari_items for a specific item id. Minimum viable.

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