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

Goes well beyond the annotations (which only mark this as a non-read-only, non-idempotent, non-destructive write) by disclosing the 50 MB size cap, the cost profile (free, no credits), the ephemeral-vs-persistent consequence of `saveAs`, and the shape of the result. These are exactly the traits annotations cannot express.

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?

Every sentence earns its place: capability, mechanics of `path`, the return value's use, the persistence toggle, and two hard limits (size, cost). The core capability is front-loaded and there is no filler.

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 still tells the agent the return value (a URL usable in render_video), the size ceiling, and the cost, which is enough to invoke this 5-parameter tool correctly. Nothing call-critical is missing.

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 coverage is already 100%, so the baseline is 3, but the description adds real meaning: `path` causes the server to read and upload the file for you, and `saveAs` controls whether the asset is discoverable later. `kind` and `contentType` are left to 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?

States a concrete verb and resource — put a local image/video/audio file where a render can reach it — and names the downstream consumer (render_video) and the library concept, which separates it from the render_* siblings and from browse_library. An agent can tell what it does and what it produces (a URL) without opening the 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?

Gives explicit conditional guidance for `saveAs` (add it to persist, omit it and the URL still works but nothing lists it later) and ties the output to render calls. It does not explicitly compare `path` vs `contentBase64` in the description, though the schema covers that choice.

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