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

With no annotations, the description carries the full burden and does well: it discloses the cost model ('1 credit per compared domain with data'), tier limits (3 Free / 30 Pro), and a fallback behavior ('fetches traffic when monthly visits are missing'). It stops short of describing failure modes or full return structure.

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?

Five short sentences, front-loaded with purpose, then output, then cost and limits. Efficient with no filler, though the trailing 'Use for 批量对比' is redundant with the tool name.

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 one-parameter tool with no annotations and no output schema, the description supplies the essentials an agent needs: cost, tier caps, and a partial return description ('scale and registry'). Exact fields of the comparison result remain unspecified.

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% for the single 'q' parameter, so the comma/newline delimiter syntax and de-duplication rule are already documented in the schema. The description adds no format detail beyond that, so the 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?

States a specific verb and resource ('Compare domains side by side') and hints at output ('Returns scale and registry'). It does not explicitly distinguish itself from the sibling compare_tld, so an agent must infer the domain-vs-TLD split.

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?

'Use for 批量对比' merely restates the tool name (bulk compare) rather than giving when-to-use conditions. It never mentions compare_tld or any alternative, and gives no exclusions despite the Free/Pro domain caps creating a clear selection boundary.

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