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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe-read profile is covered. The description adds pagination behavior ('支持 page_token 翻页') and the return shape ('频道摘要'), but says nothing about rate limits, auth, or result truncation. Adequate given the annotation coverage, but not rich.

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?

A single dense sentence that front-loads the core action and appends routing guidance; every clause carries information. Slightly crowded with three semicolon-separated ideas but no filler.

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 an output schema, full param coverage, and safety annotations, the description only needs to add routing and pagination context, which it does. It stops short of explaining error/empty-result behavior, but nothing essential to invocation is missing.

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%, and the schema itself documents keyword format (what NOT to pass) and page_token chaining semantics in detail. The description adds no parameter meaning beyond the schema, 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?

The description states a specific verb+resource ('按关键词搜索 YouTube 频道或创作者') and scopes the return ('返回频道摘要'). It also distinguishes itself from siblings by pointing to channel-by-URL lookup and video search, so an agent can route correctly without opening schemas.

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 clear routing conditions: use this for keyword channel search, use channel-profile reading when a homepage link already exists, and use video search for videos. The alternatives are described by function rather than by exact sibling tool name, so it's slightly below fully explicit.

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