extend_video

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

With no annotations, the description carries the full burden. It usefully discloses the async nature (task id + status) and that output URLs come back, which hints at a job-submission/polling workflow, but says nothing about authentication, cost, or that it is a long-running/billable operation.

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 tight sentences with the core action front-loaded and the return contract stated immediately after. No filler, though it is perhaps too terse for an 8-parameter async tool.

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?

Describing the return values is valuable given no output schema exists. However, for a task-creating tool with 8 parameters, no annotations, and 5 siblings, it omits the usage conditions and the required-parameter contract an agent needs to call it 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 description coverage is 75%, so most parameters are at least typed in the schema, and the 'wait' field explains polling behavior. The description adds no parameter meaning at all: it never mentions the required source_task_id or the roles of prompt, seeds, watermark, callback_url, or timeout.

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 and resource: creating a Veo 3.1 task on RunAPI that extends a video. This is clearly distinguishable from upscale_video, though it never contrasts itself with the similarly task-creating sibling text_to_video.

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?

No guidance on when to choose this over text_to_video or upscale_video, nor any prerequisites (e.g., an existing source task to extend). The parenthetical '(extend video)' only implies the use case rather than stating it.

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