list voices

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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered; the description adds genuinely new behavioral detail that a voice with a non-null restriction cannot synthesize speech and must be avoided. It also clarifies the id-vs-provider-voiceId distinction, which prevents a likely misuse. The trailing 'Read-only.' merely restates the annotation, so it earns no credit but does no harm.

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?

Front-loads the core purpose and the returned fields before the usage directives, and every clause carries actionable information (id fidelity, clone check, restriction rule, sibling exclusion). It is dense and somewhat run-on, packing several directives into one long sentence, but there is little filler.

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 single-parameter read-only list tool with no output schema, the definition covers purpose, filtering, returned fields, downstream id usage, and the restriction edge case. Nothing an agent needs to call it correctly or interpret results 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 100% and the single enum parameter is fully documented in-schema ('Only elevenlabs is accepted; omit to list every voice'). The description mentions provider voices but adds no filtering semantics beyond the schema, so baseline 3 applies.

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 a specific verb and resource ('List the text-to-speech voices') plus scope ('this organization can use: premade ElevenLabs voices plus voices it has cloned') and enumerates the returned fields. It also explicitly excludes adjacent resources ('Not for lipsync models; use models_list'), so an agent can separate it from siblings without opening a schema.

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?

Gives concrete when-to-use triggers ('when speech comes from a script'), names the downstream tools to pass ids to (lipsync_create, speech-previews_create), warns to check for an existing clone before cloning again, and provides an in-tool exclusion rule for voices whose restriction is set. It also names models_list as the alternative for lipsync models.

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