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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), so the bar is lower, yet the description adds genuinely useful behavior: it is asynchronous ('starts the edit and returns an id right away'), the original is preserved, and output lands in the Xenition library. It does not mention cost, rate limits, or 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?

Three tight sentences: trigger first, then async behavior and polling target, then the non-destructive guarantee. No filler and every clause carries information.

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 mutating, open-world tool with an output schema present, the description covers everything an agent needs: when to call it, that it returns an id immediately, how to learn when the result is ready, and that the source video survives. Return-value detail is rightly left to the output schema.

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 coverage is 75%, so the schema carries most of the load, but the description restates the operation vocabulary in user-intent terms (captions, enhance, matte, jumpcut), which helps map a natural-language request onto the enum-less operation string. It adds nothing for title or language beyond 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?

The description opens with a precise trigger and resource ('an existing video improved') and enumerates the four concrete capabilities: burned-in captions, enhanced picture/sound, background removal, and jumpcut silence removal. That set of operations cleanly distinguishes it from create_video (new video) and edit_image (still image) among the siblings.

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?

It gives an explicit when-to-use condition ('when the user wants an existing video improved') and routes the agent to video_status for readiness checking. It stops short of an explicit exclusion ('do not use for new videos – use create_video'), which is the only gap.

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