Fetch Bilibili video metadata—title, uploader, duration, summary, and subtitle availability—without downloading. Quickly judge if a video is worth watching.
看一个 B 站视频的元信息（不下载）：标题、UP 主、时长、简介摘要、有没有字幕。用于判断值不值得看。
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | B 站链接（含 b23.tv 短链） |
Changes observed during successful MCP inspections.
v0.7.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations supplied, the description carries the full behavioral burden. It does disclose that nothing is downloaded (an implicit read-only/no-side-effect signal) and that the description is only a summary ('简介摘要'), which usefully implies truncated content. It says nothing about authentication, rate limits, failure modes for invalid or region-locked links, or whether subtitle presence means availability versus fetchability.
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 clauses with zero waste: the returned fields are front-loaded, the 'not a download' qualifier appears immediately after the verb, and the use case closes the sentence. Nothing could be removed without losing information.
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 single-parameter lookup tool with no output schema, the description compensates by enumerating the concrete return fields, which is exactly what an agent needs to decide whether to call it. Absence of annotations means the safety/error profile is left unstated, which is the only meaningful gap.
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?
There is exactly one parameter with 100% schema description coverage, and the schema already explains it takes a Bilibili URL including b23.tv short links. The description adds no further meaning about accepted URL forms or normalization, so the baseline of 3 applies when the schema does all the work.
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?
Names a specific verb and resource ('看一个 B 站视频的元信息') and enumerates exactly what comes back: title, uploader, duration, description summary, subtitle presence. The parenthetical '（不下载）' implicitly contrasts it with the download/watch sibling, but does not name bili_video_watch outright, so the differentiation requires a small inference.
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?
'用于判断值不值得看' states a concrete use case, establishing clear context for when to reach for this tool rather than a downloading one. It stops short of explicitly routing the agent to bili_video_watch when full playback or media retrieval is wanted, so there are no stated exclusions or named alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.