video_brief

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

With no annotations, the description carries the full burden and does well: it discloses subtitle-first sourcing (0 media download), ASR fallback only when subtitles are missing, truncation behavior on long videos, and context-cost warnings for full mode. Gaps remain on the undocumented flags (refresh, scan_cuts, model) and on whether results are cached or how errors surface.

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?

Front-loaded with the default behavior and output shape, then cost warning, then source strategy, then fallbacks. Dense but each line carries operational information; only the duplicated full/level instruction is redundant.

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?

No output schema and no annotations, so the description must cover a lot for an 8-param tool. It adequately covers the main path (URL → digest/full) and the visual-follow-up split, but leaves refresh, scan_cuts, and model behavior unexplained for an agent to call those correctly.

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% across 8 params, so the description must compensate and only partly does: it explains full, level, lang, and prompt with concrete values/examples. model, refresh, and scan_cuts receive zero explanation, and the overlapping full=true vs level='full' wording creates mild ambiguity about which switch to use.

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+resource ('看一个视频') and defines the default deliverable precisely (章节 + 关键句 + 全文路径, ~1.5k 字) plus the alternate full-report mode. It distinguishes itself from video_sheet/video_frames, though several near-siblings (video_full, video_watch) are never differentiated.

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?

Explicit when-to and when-not guidance: default digest, use level='full' only when a full report is truly needed and it '长期占用上下文，慎用', long >20min no-subtitle videos stop at chapter suggestions unless full=true is passed. It also routes the agent elsewhere ('需要看画面再用 video_sheet / video_frames') and warns against a bad alternative ('不要下整片').

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