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

The annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld). The description adds billing behavior that the annotations do not provide: ¥0.1 per call, billed only on success, with automatic refund on failure or empty results, which materially affects retry decisions. The returned payload is also described, which helps because there is no output schema.

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?

Three sentences with no filler: purpose and returned fields come first, then usage scenarios, then billing. Each sentence contributes information that the annotations and schema do not already provide.

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, listing the return fields is essential, and the description supplies them in addition to cost and refund behavior. Only minor details are absent, such as what an empty or private video returns and how one extracts the video_id, which keeps it short of full completeness.

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%, and both parameters (_token and video_id) are documented in the schema, so the schema handles parameter documentation. The description adds no additional meaning about parameters and does not explain the video_id format or the header alternative, so baseline 3 is appropriate.

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?

Uses a specific verb and resource ("获取YouTube视频详情") and enumerates exactly what is returned: title, view/like/comment counts, channel info, duration, publish time, and description. The agent can distinguish this tool from sibling tools such as yt_keyword_search or yt_post_comments by its emphasis on details, though it explicitly names no sibling.

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 states concrete use cases: analyzing engagement for a single item, putting material into storage, and serving as the starting point for batch tasks. It gives no explicit when-not-to-use guidance and no named alternatives, so an agent has to infer which tool to choose by comparing names.

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