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

Annotations only indicate non-read-only, so the description carries the burden. It discloses that Gemini reads frames and auto-generates metadata, that scanning takes about 15 seconds, that callers should poll list_brand_videos, and that films reference the video by name. This is meaningful behavioral context beyond the bare annotations.

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 compact and front-loaded, with the core purpose in the first sentence and supporting behavioral detail in the following sentences. Each sentence contributes either usage context, processing behavior, or differentiation. It is slightly dense, but not padded.

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 six optional parameters and an output schema, the description sufficiently covers the tool's behavior, asynchronous scanning, and how the asset is later used. It would benefit from explicitly noting the URL/base64 choice or size limits, but those are already captured in the input schema, so no critical guidance 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 description coverage is 100%, so the baseline is 3. The description adds some nuance by explaining that even without a description, Gemini auto-generates 'what it shows, when to use it, tags and the best moments,' which maps conceptually to the use_when, tags, and description parameters. However, it does not add new per-parameter semantics beyond 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 opens with a specific verb and resource: 'Add a product demo, walkthrough or footage to Brand DNA.' It clearly distinguishes itself from sibling upload tools by explaining that videos belong to films and stills come from pictures, so an agent can separate this from upload_media or upload_logo.

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?

The description gives clear context: use it to add video assets to Brand DNA, and films will play it when a brief names it. The final sentence 'Videos are for films; stills are painted from pictures' provides a useful exclusion against image uploads, though it does not explicitly name alternative tools or state when not to use it.

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