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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuine context beyond that – the login requirement, that the transfer URL must carry the same Bearer auth as MCP and expires, and that preparation ≠ successful upload – but much of it pertains to sibling upload tools rather than this one.

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 dense run-on paragraph packs useful preconditions but mixes this tool's behavior with instructions for other tools (transfer URLs, upload receipts), so material that doesn't belong to this tool dilutes the front-loaded content.

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 zero-param read tool with no output schema, the definition supplies surrounding context but never states what the limit response contains (which formats, which byte ceiling) or how it should be consumed. Enough to call it, not enough to know what comes back.

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?

Zero parameters, so the baseline is 4; there is nothing for the description to clarify or compensate for. No parameter meaning is added or needed.

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 actual function is buried mid-sentence in the imperative "查询格式/字节上限" (query allowed formats and byte limits). Most of the text describes the surrounding file-upload workflow rather than what this tool returns, so the purpose is present but not clearly front-loaded or differentiated from the many prepare_*_upload and get_signup_file_download siblings.

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 implies sequencing (query limits first, then compute size/SHA-256, then act only after an HTTP success receipt) and states 【需登录】 as a precondition. However it never names an alternative tool or states when NOT to use this one, so guidance is implied rather than explicit.

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