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

readOnlyHint=true already declares this is a safe read, so the bar is lower. The description adds genuinely useful behavior semantics — multiple keywords are ANDed, and only currently purchasable items are returned — but says nothing about pagination, default sort, or result ordering.

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 short sentences, front-loaded with the purpose and followed by the one non-obvious query rule. No padding, though the second sentence could be attributed more clearly to the 'q' parameter.

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 six parameters, zero schema descriptions, and no output schema, the definition should explain the filters and pagination and at least hint at the result shape. It covers only the keyword semantics, leaving an agent unable to know what sort, location, or price bounds actually do.

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 0% across six parameters, so the description carries the full burden and only explains 'q' (space-separated, all must match). page, sort, location, min_price, and max_price receive no meaning at all, leaving five parameters entirely undocumented.

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 and resource ('搜尋可買的二手商品') and adds a scope qualifier (only items that are purchasable). It is distinguishable from get_listing by being a search rather than a single-item lookup, but it never names a sibling or explains the boundary explicitly.

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?

There is no guidance on when to use this versus get_listing or list_my_listings, and no mention of preconditions or exclusions. The only usage-adjacent sentence describes keyword syntax, not tool selection.

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