kling_extend_video

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

With no annotations, the description bears the full behavioral burden. It discloses that the operation is asynchronous by promising a returned Task ID and the callback_url param documents webhook notification. It does not cover permissions, cost, whether the extension is reversible, or rate limits, so meaningful gaps remain.

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 purpose followed by scannable use-case bullets; every line is relevant. The second sentence ('adding more motion and content after the original video ends') and the Returns block restate information already conveyed by the title or the output schema, costing some brevity.

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 an 8-parameter tool with an output schema present, the description needn't explain return values yet still gives a brief summary. Combined with the 100% schema coverage and explicit use cases, an agent has enough to call it correctly; only the async/permission behavior remains under-specified.

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 all 8 parameters are already documented in the schema, including enums, defaults, and the 5/10 second duration constraint. The description adds no parameter-level detail beyond this, which is the expected baseline 3 when the schema does the heavy lifting.

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+resource ('Extend an existing video') and clarifies scope: continuing a previously generated video rather than creating a new one. It implicitly separates itself from siblings like kling_generate_video by requiring a prior video_id, but never names an alternative explicitly.

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 'Use this when' block gives three concrete scenarios (video too short, continue story/motion, build longer piece by piece) that establish clear context. However, it offers no when-not guidance or named alternatives such as kling_generate_video for fresh generations.

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