Merge a clip into a UGC ad

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

The description goes far beyond the annotations: it discloses that files are uploaded first, the merge renders in the background, the returned id is in a different id space, and the caller must poll get_video with a specific kind parameter. It also explains the status polling loop and cost lookup. No contradiction with the annotations is present.

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?

Every sentence earns its place and the most important information is front-loaded: the operation, inputs, and output. The description is dense but readable, and the polling instructions are specific without being padded. It is a model of efficient tool documentation.

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 no output schema, the description fully explains the return value (merged_video_id), the id-space distinction, the required polling behavior, and the follow-up download call. It also covers preconditions, cost, and asynchronous rendering. Nothing essential for a caller to use the tool correctly is missing.

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 describes all four parameters at 100% coverage, so the baseline is 3. The description adds important extra meaning: it clarifies that 'video' is a clip id whose return id is an AD id in a different namespace, and that local file parameters imply an upload step. This exceeds the schema's basic descriptions without being exhaustive.

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 the operation: merging a completed clip, app screen recording, hook text, and optional music into a final UGC ad. It names the exact inputs and output, and the CLI equivalence ('clipugc videos merge') removes ambiguity. This also differentiates it from sibling creation tools like create_clip or create_motion_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 provides clear context for when the tool is appropriate: the clip must have status 'completed', costs can be checked via get_credits, and the result is an ad id rather than a clip id. It does not explicitly state when not to use it or name alternative tools, but the prerequisites and workflow give strong practical guidance.

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