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

No annotations are provided, so the description carries the full behavioral burden. It does reveal useful context, namely that results are ranked by three named signals, that the output is capped at five songs, and that music licensing must be verified separately. It still leaves unstated the return shape, whether keyword filtering interacts with scope, and what happens when fewer than `limit` candidates exist.

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 three compact sentences, with the action and ranking criteria front-loaded, followed by the scope list and the licensing caveat. Nothing is wasted, though the bare scope enumeration could be tightened with a few words about what each mode targets.

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 4 parameters, zero schema coverage, no annotations, and no output schema, the description has to do most of the work. It covers the purpose, the ranking signals, the scope enum, and the limit cap, but leaves both remaining parameters and the returned fields undocumented, so an agent still has to guess.

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 0%, so the description is the only source of parameter meaning. It documents the five valid `scope` strings, which the schema omits, and implies a hard cap of five on `limit`. It says nothing about `keyword` matching behavior or what `require_playlist_video` filters, leaving half the parameters unexplained.

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 first sentence names a specific verb (探す) and resource (歌ってみた候補) and even explains the ranking inputs: original-song popularity, recent competitor count, and reaction at roughly six hours after release. That distinguishes it from siblings like search_live_streams or get_game_trends. A related sibling, search_tubesaku_context, could overlap, but the description never states how the two differ.

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 five scope values suggest the intended situations (low_supply, no_recent_covers, shorts_growth, popular_covers, all), so the agent gets an implicit sense of when each one helps. However, the description never says when to choose this tool over the sibling search tools, gives no prerequisites, and explains none of the modes.

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