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

Annotations already declare readOnlyHint=false and destructiveHint=false. The description adds real value beyond that by stating 'Saves the clip only, no render,' which tells the agent about persistence scope and the absence of a render step. It does not say whether the previous title is recoverable or point to undo_edit, which keeps it from a 5.

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?

Two sentences, with the usage trigger front-loaded and the parameter format note following. Every clause carries information an agent needs; nothing restates the tool name or title.

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?

An output schema exists and annotations cover the safety profile, so the description's job is mostly the persistence note and style format, both of which it supplies. It could be more complete about overwrite behavior and recoverability, but nothing essential for calling the tool is missing.

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 only 50%, so the description carries partial burden. It compensates well for `style` by explaining the accepted formats ('white box', 'black box', 'lime word', or a title template id) and implies the meaning of `on` through 'turn on or off'. The `text` and `clip_id` semantics are already documented 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?

The description names a specific verb and resource ('reword, turn on or off, or restyle the title card at the top of a made clip'), which clearly separates it from caption-editing siblings like edit_captions and set_caption_style. It stops short of explicitly naming the sibling it could be confused with, so it lands at 4 rather than 5.

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 opening clause ('Use this when the person wants to reword, turn on or off, or restyle...') gives concrete trigger conditions tied to the three user intents. There are no explicit exclusions or named alternatives, but the intent framing is strong enough for correct routing.

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