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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely new behavioral context — pricing at ¥0.1 per call, billed only on success with automatic refunds on failure or empty results — which materially affects retry strategy. It does not explain how the pagination token is chained or when to stop paging, leaving a behavioral gap.

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?

Four compact sentences, front-loaded with the resource and returns, then the usage condition, then pricing. No filler, though the pricing sentence is placement-heavy relative to how often an agent would need it before the first call.

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?

There is no output schema, yet the description compensates by enumerating the returned fields, and it discloses billing so cost-aware agents can plan retries. The one missing piece is where continuation_token originates and how paging terminates, which matters for a pagination 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?

Schema coverage is 100%, so the baseline is 3, and the schema already documents both _token and continuation_token. The description alludes to a prerequisite ID that is not actually a parameter of this tool and does not clarify that continuation_token is carried over from a prior response, so it adds no real semantic depth 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 states a specific verb and resource — paginating and returning second-level (reply) comments — and enumerates the fields returned (body text, like count, replier info, timestamp). It implicitly separates this from top-level comment fetching by saying the main comment ID must be obtained first, but it never names the sibling tool (yt_post_comments) that supplies that ID.

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?

It gives a clear use case (tracking secondary discussions and points of controversy) plus a hard prerequisite (obtain the main comment ID first), which is exactly the sequencing an agent needs. It stops short of naming alternatives or stating when not to use it, so it is not a full when/when-not/alternative treatment.

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