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

Annotations already establish the safety profile (readOnlyHint=false, destructiveHint=false, non-idempotent), so the bar is lower. The description adds real behavioral value on top: the return payload (short-lived PUT URL, headers, uploadIntentId), the required follow-up step, and the important constraint that the server cannot read a local filesystem path. Auth requirements and URL expiry semantics beyond 'short-lived' are not stated.

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 tightly packed sentences with no filler; the trigger condition, the return contract, the next step, and the filesystem constraint are all front-loaded in roughly the order an agent needs them.

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?

An output schema exists, so return values need not be explained, yet the description still summarizes them usefully. Combined with the workflow sequencing and the local-path caveat, an agent has enough to invoke this correctly; the only missing pieces are failure modes and parameter constraints that the schema does not supply.

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 description coverage is 0% across four parameters, so the description carries the burden. It partially compensates by enumerating the accepted media kinds, which maps to most of the category enum, and by clarifying via the 'local filesystem path cannot be read' note that fileName is a name rather than a path. It says nothing about sizeBytes limits or the expected contentType format, leaving genuine gaps.

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 specific verb and resource ('prepare a media upload') and immediately names its counterpart, finalize_media_upload, making the two-step flow unambiguous. It also enumerates the supported asset kinds (image, video, document, audio, voice), so an agent can distinguish this from the unrelated attach_media/attach_media_to_draft 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?

Gives a clear when-to-use trigger ('uploading a local image, video, document, audio or voice file') and spells out the required follow-up call to finalize_media_upload. It does not, however, explain when to prefer this over siblings such as attach_media or attach_media_to_draft, so the routing decision is only partially covered.

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