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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the mutation and safety profile is covered structurally. The description adds the supported-media constraint ('Only image and video uploads are supported') and that it returns URLs, but says nothing about auth prerequisites, file size limits, or what happens on repeated uploads.

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 action, then usage guidance, then the return contract in four short sentences. Efficient, with only mild redundancy between the opening line and the return-value sentence.

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 re-explained, and annotations cover safety. But for a tool with an empty input schema and a closely named sibling in the same flow, the description omits the one thing an agent most needs: how media is provided and when to reach for upload_media rather than prepare_media_upload.

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?

There are zero parameters, which sets the baseline at 4. However, the input schema is an empty object with additionalProperties=false, and the description never explains how the media is actually supplied to the call - that mechanism is left entirely implicit.

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 ('Upload an image or video asset') and adds the intended downstream purpose ('for later operations'). It does not distinguish itself from the sibling prepare_media_upload, which appears to be part of the same upload flow, so an agent cannot tell the two apart from the text alone.

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 trigger condition ('when the user needs to provide media that will be reused in later tool calls') plus two concrete example flows (Facebook ad image/video asset, Google Ads creative flow). No exclusions or guidance on how it relates to prepare_media_upload or run_operation.

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