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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe-read profile is covered. The description adds genuinely useful context by disclosing the billing cost ('호출당 10포인트') and that per-quality cost estimates are returned, but says nothing about rate limits, auth, or failure modes for private/unavailable videos.

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 core sentence front-loads what is listed and what is returned. The full Korean restatement and the bracketed point-cost note add bulk but serve a bilingual, cost-sensitive API audience, so the duplication is defensible rather than wasteful.

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 single-parameter read tool with no output schema, the description adequately enumerates the returned fields (resolution, fps, codec, size, audio formats, per-quality cost), so an agent knows what to expect. Minor gaps remain around pagination and error behavior for non-public videos.

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% and the single url parameter is fully documented in the schema (URL or 11-char video ID). The description adds only the 'public YouTube video' constraint, which is marginal value beyond the schema; baseline 3 applies.

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 ('List') and a precisely enumerated resource (downloadable video qualities: resolution, fps, codec, size, audio formats, cost per quality) for a public YouTube video. This clearly separates it from download_youtube_video or youtube_audio_download, though it never names a sibling to make the contrast explicit.

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?

There is no when-to-use guidance and no mention of alternatives or prerequisites. The likely workflow (call this before download_youtube_video to choose a quality) is left entirely to inference, and the 'public' restriction is the only contextual hint.

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