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

Annotations already declare destructive=true, readOnly=false, idempotent=false, openWorld=true, so the agent knows this is a non-idempotent write. The description adds that it submits an asynchronous 'Builder task' with a fixed collector id, but does not disclose the async task-id workflow (implied by siblings scraper_task_status/scraper_task_result) or what resources the download consumes.

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?

Two sentences; the trigger conditions and the core action are front-loaded. The repetitive keyword enumeration ('YouTube 视频文件、YouTube 视频下载、YouTube video file、视频文件') is somewhat padded but serves a routing function.

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 an 8-parameter, non-idempotent, destructive task-submission tool with no output schema, the description should explain that it returns/queues an async task and how results are retrieved. It covers the trigger and the collector id but leaves the task lifecycle and return behavior unexplained.

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 every parameter (bitrate, resolution, codecs, subtitles_language, selected_only) is documented in the schema with defaults and allowed values. The description adds nothing about parameter meaning beyond restating the fixed collector identifier, so the 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+resource: 'submit a YouTube video file collection Builder task' with a fixed collector identifier 'youtube_video_by-url'. This lets an agent distinguish it from siblings like youtube_audio, youtube_transcript, and youtube_video_post, though the leading trigger-keyword list dilutes the core statement.

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?

It enumerates trigger phrases ('video file', 'download', combined with collect/scrape/crawl/fetch/extract/download), which implies when to fire, but never says when NOT to use it or names a specific alternative (e.g. youtube_audio for audio-only or youtube_transcript for captions). Usage is implied rather than contrasted.

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