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

Annotations declare mutating (readOnlyHint=false) and non-idempotent, and the description adds genuinely useful behavior beyond them: bytes go straight to storage and never through Mellow, and the call yields both a PUT target and a media URL for the follow-up post. It omits how long the signed URL lives or whether it is single-use, which matters for a non-idempotent operation.

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?

Two tight sentences with no filler; the primary output (signed PUT URL) is front-loaded and the usage qualifier follows immediately.

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?

With no output schema, the description carries the burden of explaining the return value, and it does so well (PUT URL + media URL for the post). The main gap is operational detail about URL lifetime and whether a new call is needed per upload, which a non-idempotent upload flow would benefit from.

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?

The tool takes zero parameters, so the baseline is 4. The description correctly implies the caller supplies nothing up front and instead receives the destination URL, which matches the empty schema.

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 makes clear this returns a signed PUT URL plus a media URL for later use in a post, which is a specific and actionable purpose. It does not name the sibling it replaces (register_media) explicitly, so it is clear but not fully differentiated from alternatives in the toolset.

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?

"Use this for anything you hold as bytes, and for any video" states the condition for choosing this tool over an alternative path. It implies but never names the URL-based alternative (likely register_media), so the routing guidance is clear but not fully explicit.

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