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

Annotations already cover read-only/idempotent/closed-world, so the description isn't burdened with safety. It adds genuinely useful context beyond them: every voice is multilingual (~30 languages), language selection is driven by the input text rather than a parameter, and there is no cost. That last point matters for an agent deciding whether to enumerate voices speculatively.

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 short sentences, zero filler, with the consumer relationship stated first. Nothing to trim and nothing buried.

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?

There is no output schema, and the description never hints at what a voice entry contains (name, id, gender, style) or that the returned identifier is what speech_synthesize expects. An agent knows why to call it but not what it will get back or how to feed the result forward.

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?

Zero parameters, so the baseline is 4. The description even clarifies a semantic point an agent might otherwise expect as a parameter: there is no language argument because the text determines the language.

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?

States the resource (voices) and ties it explicitly to the consumer tool speech_synthesize, making the relationship to its sibling unambiguous. The verb 'list' comes from the name rather than the description, but the intent is unmistakable.

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?

Implies you call this to pick a voice before calling speech_synthesize, but never states when to call it, that it takes no inputs, or that no other tool returns voice options. Usage is inferable rather than directed.

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