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

Annotations indicate a non-readonly, non-idempotent, non-destructive write, and the description adds consistent context: login required, external URL is mirrored into storage, and size/type/SSRF validation applies. It doesn't cover rate limits or quota, but the key behavioral traits are disclosed without contradicting the 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?

Three short labeled sections (auth+operation, when/how, limitations) carry no filler. The most critical information is front-loaded, and each sentence earns its place.

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 two-parameter upload helper with no output schema, the description states the essential return value (stable image URL), the auth requirement, the validation limits, and the exact downstream tools that consume the result. Nothing needed to call it correctly 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%: sourceUrl is documented as 公开 http(s) URL and kind as 用途（决定存储分类）with enum and default. The description mainly repeats the parameter constraints and adds downstream field mapping, but it does not materially extend the schema's parameter documentation.

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?

Description uses a specific verb and resource: 把公开图片 URL 镜像进独行录存储，返回稳定图片地址. It clearly distinguishes this upload helper from downstream update/create tools by framing it as the prerequisite step.

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 【何时用】 section gives an explicit trigger ('要给头像/logo/封面/图集/活动封面设图时') and a concrete sequence: upload first, then pass the returned url into update_my_profile/update_my_product/create_product/create_organizer_activity. The 【限制】 section also states valid inputs (public http(s) only), preventing misuse.

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