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

The description adds substantial information beyond the annotations: billing is metered by duration and resolution, timeout recovery must reuse the original idempotency key and unchanged parameters, and erasure defaults to the whole frame. This complements the annotated idempotentHint and destructiveHint=false and explains why the idempotency key matters. It stops short of saying what the call returns or how long processing takes.

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?

Four compact sentences, front-loaded with the purpose, then the region rule, then billing, then retry. Every sentence carries operational information and nothing is redundant. It is dense to the point that the region clause reads cryptically on a first pass.

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 14-parameter asynchronous submit tool with no output schema and no parameter-level schema documentation, the definition covers the highest-risk semantics (cost, retry safety, region rule) but leaves the response shape, the mode enum, and four optional fields unexplained. It is adequate to submit a call correctly in the common case, but not complete.

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?

With 0% schema description coverage across 14 parameters, the definition does real work: it explains the x1/y1/x2/y2 all-or-nothing region rule, justifies width/height/duration through the billing model, and motivates idempotencyKey via the retry protocol. However, the mode enum (normal vs protect), removeAudio, coverUrl, and fileName receive no explanation anywhere, leaving several parameters semantically undefined.

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 names a concrete verb and resource (submit a task that removes hard subtitles or on-frame watermarks from video) and states the default behavior of full-frame erasure. It is clear on its own, but it does not differentiate itself from the sibling remove_video_watermark, which appears to overlap in scope, so an agent must still infer which tool to use for watermark removal.

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 explicit conditional guidance for the crop parameters (fill x1/y1/x2/y2 only when the user explicitly supplies a region) and a retry protocol after a timeout. It gives no guidance on when to use this tool rather than estimate_subtitle_cost, quote_media_task, or remove_video_watermark, and no prerequisites are stated.

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