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

Annotations already establish readOnlyHint and openWorldHint, so the bar is lower; the description still adds meaningful behavior beyond them by declaring that no video/user results are returned and that pagination is unsupported. That 'no pagination' constraint is the kind of trait an agent would otherwise assume wrongly for a search tool.

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?

One compact sentence with the primary action front-loaded, followed by the two exclusion clauses. No filler, and each clause carries operative 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 one-parameter, read-only suggestion endpoint with annotations and an output schema, the description covers what an agent needs: purpose, exclusions, and no pagination. Only minor extras such as result language or typical suggestion count are absent.

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% for the single parameter, and the schema description already forbids links and pagination tokens. The description only restates the keyword's expansion purpose, adding little 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 pairs a specific verb and resource ('获取好看视频搜索联想词') with explicit negative scoping ('不返回视频或用户结果'), which directly distinguishes it from siblings like haokan_search_videos and haokan_search_users without opening either schema.

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 clearly states the use case ('用于补全或扩展关键词') and rules out the search-result interpretation, implicitly routing result queries to the search_videos/search_users siblings. It stops short of naming those alternatives explicitly, so it is 4 rather than 5.

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