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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds cost behavior (¥0.2 per call, charged only on success, refunded on failure or empty results), which is genuinely useful context an agent cannot get from schema or 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?

Four short sentences, front-loaded with the action, then return fields, then use cases, then billing. No sentence is redundant, and the return-field sentence earns its place because there is no output schema.

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 no output schema, the description correctly spells out return fields (ID, title, price, supplier), and it covers cost and failure handling. It stops short of stating any input constraints on the image URL or expected result-count/pagination, which is a minor gap for a two-parameter search tool.

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 coverage is 100% — image_url and the optional _token are both documented in-schema. The description adds no meaning about the image URL (e.g., public accessibility, format) beyond what the schema states, so the baseline of 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?

States a specific verb and resource: searching 1688 products via an image, with the returned fields enumerated. The image-modality framing ("用图片找同款") implicitly separates it from the keyword sibling item_search_1688, though no sibling is named 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?

Gives three concrete usage scenarios: finding same-style items by image, reverse-sourcing a supplier, and price comparison. It does not state when to prefer the keyword-search sibling instead, so the boundary is only implied.

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