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

Annotations already establish readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the bar is lower. The description adds that podcast tabs may be absent on some channels (implicitly, via 'or its podcasts'), but it says nothing about paging behavior or result ordering for an open-world, non-idempotent listing call.

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?

Three short sentences, front-loaded with purpose and then identifier forms and the sibling hand-off. Nothing is wasted and no redundant restatement of schema fields.

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?

With a full input schema and an output schema present, the description need only cover purpose and routing, which it does. Slight incompleteness in not hinting at the meaning of a missing podcast tab or at paging, both of which are handled in the schema.

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 description coverage is 100%, so all three parameters are already documented, including the tab enum's empty-result notice and the 1–50 limit range. The description only restates the accepted channel identifier formats, adding little beyond what the schema says.

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 a specific verb and resource ('List a YouTube channel's playlists, or its podcasts') and implicitly separates itself from list_channel_videos and list_playlist_videos by naming the follow-up tool. An agent can pick this tool without opening the schema.

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?

Explicitly routes the agent forward: 'Pass a playlist's url to list_playlist_videos for its videos.' It does not state when to prefer list_channel_videos or the search_* siblings over this tool, so a small gap remains.

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