video_comments

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

Annotations already declare the tool read-only and idempotent. The description adds value by specifying the return fields (comment text, like count, author) and the cost (1+ YouTube API units, 0 Gemini units). This provides practical behavioral context beyond the 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 three sentences long, covering purpose, return data, and cost. Every sentence is informative and there is no redundancy or filler. It is well-structured and easily scannable.

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 the tool's simplicity (2 parameters), existing annotations, and presence of an output schema, the description is mostly complete. It explains the tool's functionality and cost. Minor gaps include lack of mention of pagination or potential authentication requirements, but these are not critical for basic usage.

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?

Input schema coverage is 100%, so the schema already describes both parameters adequately. The description does not add new parameter-level details beyond what the schema provides (e.g., sorting by relevance is already in the schema for max_comments). The description's mention of return fields relates to the output, not parameters.

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 it fetches top YouTube comments sorted by relevance, distinguishing it from sibling tools like video_metadata or video_analyze. It explicitly mentions the resource (YouTube comments) and action (fetch), making the purpose unambiguous.

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 provides implicit context for when to use this tool (fetching comments) but does not explicitly state when not to use it or suggest alternatives. For example, it does not mention that video_metadata or video_analyze could be used for other video data. The usage guidance is minimal.

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