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

The description discloses key behaviors: supports live and fw/user share links, returns a reusable non-empty user_id on success, and rejects work links. Annotations already cover read-only safety (readOnlyHint: true), so the description adds value by detailing the return value guarantee and input constraints. No contradiction with annotations.

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?

The description is a single, well-structured sentence that front-loads the purpose and flows logically through input types, success behavior, exclusions, and usage guidance. Every clause earns its place; no filler or redundancy.

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 one-parameter read-only tool with an output schema, the description covers all necessary context: input formats, supported link types, prohibited input, output behavior (non-empty user_id), and when to use an alternative. It is complete for the tool's complexity.

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?

The schema already provides 100% coverage for the single parameter profile_url, with the same detailed description of accepted formats and constraints. The tool description adds no new semantic information beyond what's in the schema, so the baseline 3 applies. It simply reinforces the schema.

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 clearly states the tool's function: '根据快手用户主页链接、短链接或分享文案获取用户资料' (get user profile from profile URL). It specifies the exact input type (profile URL, short link, share text) and distinguishes from sibling tools by mentioning the user_id entry and excluding work links. This is a specific verb+resource with clear differentiation.

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?

The description explicitly says '如果上一步结果已返回非空 user_id，可直接使用 user_id 入口', advising to use the user_id entry (sibling tool) when a non-empty user_id already exists. It also says '不要传作品链接' (don't pass work links), providing a clear exclusion. This is explicit when-to-use and when-not-to-use guidance with a stated alternative.

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