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

Annotations already declare readOnlyHint=false but destructiveHint=false, and the description adds real behavioral context beyond that: a 60-minute TTL, memory-only holding, and deletion after a successful tool call. It does not mention auth requirements, file size limits, or what happens on expiry/failure, so it is strong but not exhaustive for a resource-creating tool.

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 sentences, zero filler, each carrying distinct information: purpose first, then lifetime/persistence, then return values and how to use them. Front-loaded and appropriately sized.

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, and the description compensates by naming both return fields (upload_url with its HTTP PUT contract, and upload_id) plus their downstream use. For a single-parameter tool this covers everything needed to call and consume it correctly.

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 one parameter at 100% schema description coverage, the schema already documents name (including the extension, with an example). The description only says "one file" and adds no constraint or format detail beyond the schema, so baseline 3 applies.

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?

"Reserves a single-use upload link for one file" names a specific verb, resource, and cardinality constraint. None of the sibling tools create upload links, so the agent can immediately tell this is not a file-conversion operation.

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?

It states how the result is consumed: upload_id can replace content_base64 in the files argument of the file tools, which implicitly routes the agent away from inline base64. It never explicitly says when to prefer this over the base64 sibling or what size/type limits apply, so it falls short of a full when/when-not statement.

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