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

Adds real behavior beyond the annotations: the upload is moderated, there is a 3 MiB decoded cap, raw base64 is mandatory (no data URL), and a Bearer key is required for auth. What it omits is failure behavior — what a moderation rejection or oversize error looks like — and any rate limits, which keeps it off 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?

Four sentences, front-loaded with purpose, followed by format/size constraint, output usage, and the alternative transport path. Every sentence carries information, though 'Requires a key' and the repeated 'Bearer key' could be merged into one auth statement.

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?

A two-parameter tool with no output schema, and the description covers the essentials an agent needs: input encoding rules, size ceiling, auth, and that a url comes back and where to put it. Error/moderation-outcome handling is the only meaningful gap.

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?

With 0% schema description coverage, the description must carry parameter meaning, and it largely does: it explains that base64 must be raw without a data URL prefix and bounded to 3 MiB decoded, and it enumerates PNG/JPEG/WebP matching the mimeType enum. It never states parameter names or pre-decode size expectations, so a 4 rather than a 5.

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 and moderate a ... image') plus the downstream purpose ('for video generation') and accepted formats. This is clearly distinguishable from every sibling (cost estimation, generation, status, model listing), none of which handle image ingestion.

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 usage conditions and an explicit alternative path: clients with file/shell access should POST multipart to the given endpoint instead of transcribing bytes through the model. It also routes the agent downstream by telling it to feed the returned url into imageUrl or lastFrameUrl.

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