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

With no annotations present, the description carries the full burden and does so thoroughly. It discloses immediate cost effects ('new library addition costs 1 credit'), free repeats, per-item error handling ('Videos without captions are reported per-item and do not fail'), and partial failure semantics ('partial=true and an out_of_credits stopped block'). This is an unusually complete account of side effects.

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 about five sentences and front-loads the core call shape before covering cost and failure nuances. Every sentence serves a purpose, including credit warnings and workflow for channels or playlists. It is slightly dense — the balance sentence includes multiple clauses — but still efficient for this amount of behavioral detail.

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?

Despite having no output schema, the description explains per-item failures and partial success enough for an agent to understand batch side effects. It also gives a sensible orchestration path for channel/playlist usage. It could mention the normal per-video transcript structure, but that omission is minor given the strong behavioral focus.

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 the baseline is 3. The description repeats the schema's point about 'YouTube URLs or ids' and adds the 20-video limit, but it does not explain the language parameter. No additional meaning is added beyond the structured schema, so a solid baseline score is appropriate.

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 opens with a specific action and scope: 'Fetch transcripts for up to 20 videos in one call.' It clearly names the resource (YouTube transcripts) and the input format (array of URLs or ids). It also implies the plural batch nature, distinguishing it from the singular sibling get_transcript.

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 gives a clear funnel for channels or playlists: 'first list the videos with get_channel_videos / get_playlist_videos, then batch the ids through this tool.' It also explains what happens without captions and when the balance runs out. However, it never explicitly contrasts with the singular get_transcript tool, so an agent might not know when to choose this tool over that one.

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