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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered structurally. The description adds a genuinely useful behavioral caveat not present in annotations or schema: the thumbnail/homepage statistics are approximate values ('缩略统计为近似值'). It stops short of covering freshness or rate limits, so 4 rather than 5.

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 sentence, front-loaded with the purpose, then the alternative-tool rule, then the approximate-stats caveat. No filler and nothing important buried.

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?

A one-parameter read tool with full schema coverage, an output schema (so return shape needn't be described), and annotations covering safety. Purpose, input constraints, sibling routing, and the approximation caveat are all present.

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 single parameter's schema text already specifies accepted formats and the anti-patterns (content links, pure IDs). The description largely restates that, so the 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?

Names a specific verb and resource ('读取头条用户资料和主页统计') and states the accepted input form (主页链接或分享文案). It also explicitly distinguishes itself from the sibling toutiao_get_user_info_by_user_id, so an agent can choose between them 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?

Gives an explicit routing rule: when a numeric user ID is also available, prefer toutiao_get_user_info_by_user_id. The schema reinforces the exclusion set (no content links, no pure IDs), so both when-to-use and when-not-to-use are covered.

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