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

No annotations, yet the description carries the full burden well: one file per upload, single PUT only, no key/signing needed with a curl example, and a one-day lifetime. It also explains the return shape (upload_id + upload_url) since there is no output schema.

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?

Front-loaded with the core action and the return contract, then the rationale and the curl example. Slightly long but nearly every sentence adds operational value; minor trimming possible.

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?

Despite no output schema and no annotations, the description fully covers the two-step flow, the returned identifiers, the one-PUT/one-file/one-day constraints, and how to hand off to sending tools. An agent can invoke it correctly from this alone.

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 coverage is 100%, so both filename and content_type are already documented; the description largely restates the fixed-filename rule and adds little new about these two parameters. Baseline 3 is appropriate given 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 concrete verb+resource ('opens an address to send a file to') plus the mechanism (upload_url + upload_id). Distinguishes itself from the inline base64 attachment path and from the sending 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?

Explicitly says when to use it (attaching a real document, since base64 overruns for multi-page PDFs) and names the exact siblings that consume the upload_id (send_email, reply_to_conversation, forward_conversation, approve_draft). Nothing left to inference.

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