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

Annotations already establish that this is a non-read-only, non-destructive, closed-world mutation. The description adds significant behavioral context beyond annotations: changes happen without a render, scope limits the effect to selected words, hide replaces the clip's hidden stretches, reset has specific meanings, and clips with generated scenes follow the change. It stops short of covering permission needs or full reversibility, so it is strong but not exhaustive.

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?

The when-to-use guidance is front-loaded, and the length is partly justified by 32 parameters. However, nearly all parameter semantics are packed into one run-on paragraph with semicolons and parentheticals, making it hard for an agent to scan and parse the different option groups.

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?

Given the tool's complexity, the description covers the essential decision context, the main parameter families, scoping behavior, hide semantics, reset semantics, and the key sibling alternative. An output schema exists, so the description does not need to explain return values, and the remaining details are handled by the rich input 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 already high, but the description adds domain meaning: style names come from list_styles, size and position accept specific named values, caption_y can keep captions clear of a scene's drawing, hide is for stretches where a scene already shows words, scope applies styling to a word range, and words applies styling to individual words. It covers most parameter groups, though the single dense sentence is less precise than the schema for several nested options.

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 states a specific action and resource: change a made clip's captions look, including style, size, position, colour, effects, and per-word or per-range styling. It explicitly distinguishes itself from restyle_clip, so an agent can identify the correct tool without opening the schema.

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 a clear when-to-use condition: the person wants to change an already made clip's captions by hand without a render. It also names the alternative and its selecting condition: use restyle_clip only when a new video should be made straight away.

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