douyin_download

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

Annotations supply only a title, so the description carries the burden and does well: it discloses the quality-selection policy (watermark-free, H.264 preferred), the differing behavior for image galleries, the optional background-music track, manifest-based deduplication ('已下过的会自动跳过'), and that a local file path is returned. It omits any mention of whether login/auth is required, which is notable given sibling login tools.

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 compact and front-loaded with the action, then layers on quality policy, gallery behavior, music option, dedup, and return value in a single dense sentence plus a closing clause. Every clause carries information; only the '剪辑/发布' hint is arguably decorative.

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 4-parameter download tool with no output schema, the description covers selection policy, side effects on disk, dedup semantics, and the shape of the return value (local path), which is what an agent needs to chain it into editing or publishing. The main remaining gap is the absence of any authentication prerequisite, which matters here since Douyin downloads commonly require login.

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 schema already documents all four parameters, making baseline 3 appropriate. The description adds some meaning for `music` (optional, downloads an mp3 alongside) and clarifies that `target` accepts either a share link or a work ID and may resolve to a video or an image gallery, but says nothing extra about `dir` or `raw`.

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 states a specific verb and resource ('下载一个抖音作品到本地') and enumerates what gets fetched: the highest available watermark-free video (H.264 preferred) or all images for an image gallery. It does not explicitly name a sibling such as douyin_batch_download or douyin_parse, so the single-vs-batch distinction must be inferred, but the operation itself is unambiguous.

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?

Usage context is only implied: it is clearly the single-item download path, and the closing note '可用于后续剪辑/发布' hints at the downstream workflow. There is no explicit 'use this instead of X' routing to douyin_batch_download or douyin_parse, and no stated prerequisites.

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