Download a clip or ad

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

Even though annotations are present, the description adds meaningful behavioral context: it costs no credits, creates missing parent directories, downloads to a local mp4 file, and fails on incomplete videos. These details go beyond the structured annotations and help the agent predict side effects and failure modes.

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 core action and resource, followed by essential behavioral notes. Every sentence contributes useful information: kind semantics, CLI equivalence, path handling, cost, and failure condition. No filler or redundancy is present.

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 three-parameter download tool with no output schema, the description is complete. It covers what the tool does, the valid inputs, default behavior, side effects, cost, and failure conditions. An agent has everything needed to invoke it correctly and anticipate the outcome.

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?

The schema already covers all parameters at 100% coverage, so the baseline is 3. The description adds value by explaining that 'ad' refers to a merged_video_id, that output can be an absolute path with auto-created directories, and that defaults are clipugc-video-<id>.mp4 or clipugc-ad-<id>.mp4. This enhances the schema's parameter documentation.

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 clearly states a specific action ('Download') on a specific resource ('a completed clip' or 'a completed merged ad') to a local mp4 file. It also distinguishes the two supported kinds ('clip' and 'ad'), making the tool's purpose unambiguous and differentiating it from siblings like get_video or create_clip.

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 description gives clear context for when the tool is appropriate: use it after a clip or ad has completed, and it explicitly warns that it fails if the video is not yet complete. It does not name alternative tools explicitly, but the conditionality and the local-file outcome provide sufficient usage guidance.

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