video_edit

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

Annotations already flag this as a non-read-only, non-idempotent, open-world mutation, and the description adds the material facts they cannot express: the operation costs money and is billed like video_generate, output is written to a new file rather than mutating the input, and there is a wait/poll split with video_check. The input-video length ceiling (10 s) is another behavioral constraint disclosed up front.

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-loads the cost warning and the mutual-exclusivity rule before the arg list, so the highest-risk information is read first. The Args/Returns block is compact, every line adds a fact not present in the schema, and there is no filler.

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 seven-parameter, costly, async-capable mutation this covers the decision points an agent needs: which input to supply, size limits, cost gating, and how to retrieve results later. The return shape is summarized briefly and an output schema exists, so nothing further is required there.

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 0%, so the description carries the full burden and does: each of the seven parameters gets meaning plus examples (instruction like "Make it night", extension phrasing), the enum values for aspect_ratio are restated, resolution defaults are named, and the mutual exclusivity between previous_id and video_path is stated. This is meaningfully more than the bare property names in the schema.

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?

Opens with a specific verb and resource: "Change or extend a video; the result is saved as a new file." That single clause separates it from video_generate (creation) and video_stitch (joining), and the extend case is spelled out with concrete limits (adds 3-10 s, up to 40 s total).

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?

Gives explicit when-to-use routing: "Give exactly one of previous_id ... or video_path", names where previous_id comes from, and points to video_check for polling when wait_seconds expires. It also states a hard precondition — confirm with the user because it is billed — which is exactly the kind of gating an agent needs.

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