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

Beyond the annotations, the description discloses file size limits (150 MB per file, 200 MB per project), the 24-hour upload lifetime, the network requirement for the curl script, the fallback browser workflow, and the exact shape of returned values. The annotations are consistent with an upload-initialization operation that is not read-only, destructive, idempotent, or open-world in the sense of arbitrary external fetching.

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?

The description is dense and largely front-loaded, with no filler sentences. It is slightly lengthy for a single paragraph, and breaking the return values and fallback workflow into clearer segments would improve scanability.

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?

Given the tool's complexity, the description covers what the tool does, how to invoke it, what it returns, size limits, network requirements, fallback behavior, and upload duration. An output schema exists, but the description still gives enough context for an agent to use the tool 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?

The schema already has 100% description coverage for the files parameter and its id/name fields. The description nevertheless adds useful meaning by explaining that ids are what layers will use as props.asset and by providing file-size constraints not present in the 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 states a specific verb and resource: opening an upload for the user's own images, videos, audio, or fonts that are not at a public https link. It explains the downstream purpose, packing files inside the .hcmotion via create_hcmotion, which clearly distinguishes it from sibling tools.

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 explicitly says when to use this tool: files not at a public https link, such as attachments or sandbox files. It also gives a clear operational sequence, trying the script first and falling back to the page if the shell cannot reach the host, and notes the downstream create_hcmotion usage.

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