set_thumbnail

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

The description discloses file type and size limits (JPG/PNG, <2MB), which is useful. However, it does not explain the effect of the 'dry_run' parameter, whether the operation overwrites an existing thumbnail, required permissions, or error conditions. Since there are no annotations, the description bears the full burden of behavioral disclosure but falls short.

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 a single, focused sentence that is front-loaded with the key purpose. It is concise and avoids unnecessary words, though it could be slightly more structured to include parameter details.

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?

For a tool with 3 parameters, no annotations, and no output schema, the description is incomplete. It omits details on video_id format, dry_run behavior, output/return values, permissions, and error handling, making it insufficient for safe autonomous invocation.

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 description adds file constraints to 'image_path', which the schema lacks (schema coverage is 0%). However, it provides no additional meaning for 'video_id' or 'dry_run' parameters. It partially compensates for the schema gaps but leaves important parameters undocumented.

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 the action (set a custom thumbnail) and specifies file constraints (JPG/PNG, <2MB). However, it does not explicitly mention that the thumbnail is for a video, though this is inferred from the parameter 'video_id'. It distinguishes from sibling tools like 'upload_video' and 'update_video' by focusing on thumbnail setting.

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?

No guidance is provided on when to use this tool versus alternatives (e.g., 'upload_video' for video uploads), nor are there any prerequisites or exclusions mentioned. The description lacks context for appropriate usage.

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