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

Goes well beyond the annotations: it discloses the two-step handshake (returns a dedicated PUT URL, host/CLI uploads raw bytes with the same MCP credential), the server-side validation gate (size, SHA-256, format), a rejection policy for sensitive questions such as ID documents, and the prohibition on swapping keys to bypass. None of this is derivable from readOnlyHint/destructiveHint/openWorldHint.

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?

A single dense paragraph that front-loads the login/self requirement and the non-mutating scope before the mechanics. Every clause carries information, though the run-on punctuation makes it slightly harder to scan than an ideal definition.

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?

No output schema exists, and the description covers the return value (PUT URL), the auth/credential requirement, and the downstream submit_signup linkage, so an agent knows how to act after the call. The only real gap is that two of six required parameters (slug, fileName) remain unexplained.

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?

With only 50% schema description coverage, the description compensates: it ties bytes/sha256/mime to server-side validation, and 不得换key绕过 gives behavioral meaning to the key parameter. slug and fileName still carry no explanation in either place, so it falls short of full coverage.

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+resource (准备上传指定报名文件题) and immediately scopes it (不公开文件，不提交报名), which cleanly separates it from submit_signup, get_signup_file_download, and the activity-material/photo upload preparers. An agent can identify the tool without opening the 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 trigger condition (仅用户提供真实文件时) and a negative boundary (不提交报名), plus the downstream sequence (上传成功后 submit_signup 会沿用已保存附件). It stops short of naming a specific sibling alternative to use instead when the user has no real file, but the when-to-use signal is unambiguous.

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