set-thumbnail

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

No annotations are provided, so the description carries the full burden. It discloses the 50-quota-unit cost and the local file requirement, which is useful context. However, it does not mention prerequisites like video ownership, irreversibility, or response behavior, leaving gaps in transparency.

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 short, front-loaded sentences state the action and cost with zero wasted words. The description is concise and scannable, covering all essential information without redundancy.

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?

The description covers the core operation and cost, but with no output schema or annotations, it omits details about return behavior, permissions, and conflict with existing thumbnails. For a simple set operation this is adequate but not thorough, especially given the absence of explicit usage guidance.

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?

The input schema already provides clear descriptions for both parameters (Video ID and Absolute local path), so the description adds little beyond restating the local file source. With 100% schema coverage, the baseline of 3 applies; the description does not enrich parameter understanding.

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 uses a specific verb ('Upload and set') and resource ('video's custom thumbnail'), and adds 'from a local image file,' which clearly distinguishes it from related tools like update-video or set-watermark. It leaves no doubt about the tool's function.

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 implies its use case (setting a video thumbnail) and even mentions the quota cost, but it does not explicitly state when to use this tool versus alternatives or provide exclusions. No sibling tools are named, so an agent must infer usage from the purpose.

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