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

The annotations already provide readOnlyHint=true, and the description complements this by being a non-mutating list operation. It adds genuinely useful behavioral details: ordering, accepted playlist id forms, the ids_only result mode, and the rough per-page limit. This goes beyond what annotations alone communicate.

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 tight sentences with no filler: the first gives the core purpose and ordering, the second explains accepted id formats, and the third covers the ids_only mode. The most important information is front-loaded.

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 that an output schema exists and all parameters are documented within the input schema, the description covers the key behavior an agent needs before calling. It does not explain pagination flow in the sense of 'pass next_page_token for subsequent pages,' but the schema parameter already supplies that detail.

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. The description mostly restates what the input schema already documents (PL... id or URL with list=, ids_only returns ids), and the 'up to 500 per page' detail is also present in the schema's limit parameter. It adds only marginal clarifications.

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 uses a specific verb ('List') and a specific resource ('videos of a playlist') and adds the important semantic 'in playlist order.' This clearly distinguishes it from a generic video tool, though it does not explicitly distinguish it from sibling tools such as search_playlist_videos or list_channel_videos.

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 intended situation is implied: use it when you want a playlist's full set of videos in playlist order rather than a search. However, it never mentions alternatives or says 'for search, use search_playlist_videos,' so the agent must infer when this is the correct choice.

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