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

The description adds genuinely useful behavior beyond the annotations: the 64 KiB ceiling and the one-hour / 100-download expiry policy. Since annotations already declare readOnlyHint=false, destructiveHint=false and non-idempotency, the remaining gap is the consequence of expiry or name collisions (whether a re-upload under the same name overwrites) and the result of the call, which are not disclosed. That lands just above the baseline the annotations set.

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 sentences, the hard limit front-loaded, and the escalation path last. No filler and nothing repeated from the schema beyond what is needed to set the constraint.

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?

There is no output schema, so the description is the only place an agent could learn what an upload yields — an identifier, URL, or handle needed for the sibling inspect/download/delete tools — and it says nothing about the return. Everything about the write itself (size, format, expiry) is complete, but the post-call workflow is unspecified.

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 75%, and the description reinforces the most error-prone constraint by tying the 64 KiB cap to the base64 parameter and revealing the tool-level default of 100 downloads that the maxDownloads parameter can override. The visibility parameter has no description in the schema and none here, leaving one parameter's semantics unstated.

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 opens with a specific verb and resource ("Upload a file") and immediately bounds it with a 64 KiB limit and base64 encoding format, so an agent knows exactly what operation this performs. It implicitly separates itself from download_temporary_file/delete_temporary_file by the upload verb, but it never names those siblings to clarify the workflow split.

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 closing sentence "Use HTTP for larger files" is an explicit exclusion that routes the agent away from this tool when the payload exceeds 64 KiB. It does not, however, say when to prefer this tool over the sibling inspect/download tools or what to do after upload, so the guidance stops short of full routing.

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