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

Because no annotations are provided, the description must detail the operation and side effects. It states exactly what is returned (id, name, gender, accent, language) and the per-generation credit cost, which is an important behavioral fact. It does not mention pagination or caching, but for a zero-argument listing tool the disclosure is adequate.

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?

One sentence, front-loaded with the verb and resource, followed by a compact parenthetical field list. There is no filler and every phrase contributes to the agent's understanding.

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 parameters and no output schema, the description is mostly complete: it tells the agent what will be returned and includes credit cost. A fully robust definition might note that this is a read-only list or mention whether results are paginated, but those are minor absences for such a simple tool.

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?

There are zero parameters and the schema is an empty object, so there is nothing to document. The description actually enriches the output side by listing the fields and cost. Since the baseline for zero parameters is 4, this fits.

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 the exact verb 'list' and the resource 'available text-to-speech voices', explicitly enumerates the returned fields, and adds the credit-cost detail. This clearly distinguishes it from generation-tool siblings such as generate_speech or generate_image.

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 phrase 'available text-to-speech voices' clearly scopes this to TTS voice discovery and gives an implicit context: before generating speech, an agent should consult this tool. It does not explicitly name when-not-to-use or alternatives, but the context is clear.

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