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

Annotations already mark this as a non-readonly, non-destructive, non-idempotent operation, and the description adds meaningful behavior beyond them: the 1-hour link retention, that audio length is billed against the key's plan, and that longer texts take longer to process. It doesn't cover failure behavior or rate limits, but the added quota and expiry context is substantive.

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 with no filler; the core action and return value come first, followed by billing and size constraints. Every clause carries actionable 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?

With no output schema, the description correctly fills the gap by explaining the return (a link kept 1 hour) and the include_audio option. It is nearly complete for a synthesis tool, missing only error/auth expectations.

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 80%, so parameters are largely documented already. The description reiterates the 20000-character cap (also in maxLength) but adds no meaning about 'voice' resolution, 'format', or 'include_audio' beyond what the schema says, so it sits at the baseline.

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 gives a specific verb and resource ('Turn a text into speech') and states the concrete return ('a link to the audio file'), so the agent knows exactly what the call produces. It does not explicitly contrast with siblings like list_voices or get_usage, but the purpose is unambiguous on its own.

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 offers one practical guideline ('voice long texts in parts') tied to a stated constraint, which is useful. However, it never says when to prefer this tool over list_voices or get_usage, and gives no guidance on prerequisites such as needing a valid voice id first.

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