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

With no annotations, the description carries the burden. It discloses that the tool is browser-based and provides an estimate, implying approximate results. It also mentions additional features, but it does not describe limitations, required inputs, or what the output looks like in detail.

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 description is extremely concise and front-loaded with the primary function. It is structured as a clear mapping (script text -> estimated duration) plus extra features, with no fluff or redundant 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 simple calculator tool with no output schema, the description sufficiently conveys the core purpose and additional capabilities. It could be more complete by specifying output units or interaction details, but it covers the essentials.

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?

Since the input schema is empty, the description is the only source for parameter meaning. It explains that the tool uses script character count as a basis for estimation, which adds valuable context beyond the empty 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 clearly states the tool estimates video duration from script character count ('台本文字数→動画尺を推定'), using a specific verb and resource. It also mentions additional features (speech speed adjustment, duration allocation) that distinguish it from other video-related sibling tools.

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 description implies the use case (estimating video length from script text) but provides no explicit usage context, exclusions, or alternatives compared to other tools. The 'Browser-based tool' hint adds some context but does not clarify when to choose this over similar tools.

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