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

Annotations already establish a read-only, idempotent, non-destructive open-world read. The description adds billing behavior that annotations do not cover: ¥0.2 per call, charged only on success, with automatic refunds for failures or empty results. It also enumerates the returned fields, which is useful because there is no output schema. It does not cover pagination or depth limits, though.

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 compact sentences with no filler. The return-value sentence and the prerequisite are placed correctly before the billing note. One sentence could merge the return fields with the purpose statement, but nothing is wasted.

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 3-parameter read tool with no output schema, the description covers purpose, prerequisite, returned data, and cost model. It omits pagination and size limits, which matter when replies are numerous, but the agent knows enough to call the tool 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 coverage is 100%, so the two required parameters already have descriptions, and the _token fallback auth note is also in the schema. The description's only addition is the reminder that root_comment_id must be obtained first; it does not explain the ID format or how it can be obtained.

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 definition states a specific verb and resource: it fetches replies ('二级评论') to Kuaishou comments, plus the exact fields returned. It distinguishes itself implicitly from ks_post_comments by requiring a root comment ID, though it never names the sibling that supplies that ID.

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 gives an explicit when-to-use ('追踪评论区的二次讨论与争议点') and a hard prerequisite ('需先拿到主评论ID'). It does not state when to prefer this tool over an equivalent on another platform, and it names no alternatives; however, for a platform-specific tool that is acceptable.

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