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

Annotations already declare non-read-only, idempotent, non-destructive, open-world behavior, so the bar is lower; the description still adds real constraints not in the schema — per-format size limits (8 MB images, 60 MB video) and the fact that it is free. It doesn't say what happens on an oversized or invalid file, or that the resulting /u/ link is durable, which keeps it short of a 5.

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 short sentences, front-loaded with the capability and limits, then the 'you rarely need this' routing signal, then cost. Every clause carries information; even 'Free.' earns its place as a cost signal for a billable-looking upload.

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?

For a two-optional-parameter, non-destructive upload with no output schema, the description covers formats, limits, inputs, the returned /u/ link, and when to skip it. The main omission is failure behavior — what an agent should do if the file exceeds the size cap or the URL isn't public — which matters given both parameters are optional and mutually substitutable.

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 100%, so baseline is 3. The description restates both modes ('public https file link or the file as base64') and reinforces that the link must be public https, but adds no format examples, data-URL syntax, or precedence rule when both are supplied beyond what the schema already documents.

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 ('Store an image ... or a video ... in CartViral') plus the concrete outcome ('get its /u/ link for the Create tools'). It also implicitly distinguishes itself from the Create tools by noting those accept a public link directly, so an agent can tell which path to take without opening a schema.

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?

Explicitly says when NOT to use it ('You rarely need this: every Create tool also takes a public link directly') and names the alternative path. The two input modes (public https link vs. base64) are laid out as the two conditions under which the tool is appropriate.

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