get_video_thumbnail

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

No annotations provided, so the description fully informs: thumbnails expire fast (reliability), returns a list, and identifies the preferred thumbnail with is_preferred=true. No contradictions.

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?

Two concise sentences front-loaded with the primary action. Every sentence adds critical information: purpose, expiration behavior, recommended usage, and return format.

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?

Has output schema, so return details are covered. Description explains usage timing and preferred thumbnail selection. Adequate for a single-parameter, read-only tool.

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?

Single parameter video_id has no schema description. The description says 'for a video' but does not explain the expected format or source. With 0% schema coverage, the description partly compensates but lacks specifics.

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 clearly states 'Fetch fresh thumbnail urls for a video.' It uses a specific verb ('fetch') and identifies the resource ('thumbnail urls for a video'), and distinguishes itself from sibling tools by focusing on fresh thumbnails.

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 advises calling 'immediately before create_ad_creative' and using the returned URI as image_url, giving clear context for when and how to use this tool. No alternatives needed given the unique purpose.

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