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

Annotations already mark it read-only and open-world; the description adds useful behavior: images, carousels, shared videos and polls all return as posts, poll options are under `raw`, and the call costs 1 credit. It does not describe pagination behavior or auth/rate-limit details, so it is not a 5.

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?

Front-loaded and short, with useful scope and return-shape details. The opening phrase 'Channel community posts' is close to a name/title restatement, which keeps it from a 5.

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 read-only listing tool with annotations and no output schema, the description supplies key return-content context and the credit cost. It still leaves cache_max_age behavior and the single-post alternative unaddressed, so it is not fully complete.

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 67%; handle and cursor are described in the schema, but cache_max_age is undocumented and the description mentions no parameters. It adds no parameter meaning beyond the schema and does not compensate for the missing parameter.

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?

States that the tool returns a channel's Posts tab content and enumerates what counts as a post, so the resource is clear. It stops short of 5 because it does not explicitly contrast with the closest sibling, youtube_communityPost, or with youtube_channelVideos.

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 'Posts tab' framing implies when to use it, but there is no explicit when-not guidance or named alternative such as youtube_communityPost for a single post. The agent must infer routing from the resource label.

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