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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description focuses elsewhere and adds genuinely non-obvious behavior: pricing at ¥0.1/call, billing only on success, and automatic refund on failure or empty result. With no output schema, listing the returned fields is also useful disclosure. It doesn't mention rate limits or what an empty-but-successful payload looks like, so not a 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?

Four short sentences, each doing distinct work: what it does, what it returns, when to use it, and cost behavior. The purpose is front-loaded and there is no filler or repetition of the annotations.

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 simple two-parameter read-only lookup, the description covers purpose, return payload, use cases, and billing — everything needed to decide and call. The only small gap is that uid is described just as '用户mid' with no hint about format or where to obtain it, which matters slightly more given there is no output schema to fall back on.

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% (uid as '用户mid', _token as header-preferred fallback auth), so the schema already carries parameter meaning. The description adds nothing about uid format (numeric mid vs. any string) or when the _token fallback matters. Baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb and resource (获取B站UP主信息) and enumerates the returned fields (昵称、粉丝数、获赞数、简介、认证状态), which implicitly distinguishes it from the sibling bili_user_posts. The bili_ prefix plus 'UP主' makes the platform unambiguous among the many *_user_info siblings. It stops short of naming an alternative tool explicitly, so it lands just under a 5.

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 three concrete use cases — 达人筛选, 账号画像, 粉丝量级分组 — which is real when-to-use guidance rather than a restatement of the purpose. It lacks any when-not-to-use condition or a pointer to bili_user_posts for post-level data, so 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.