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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior: the fields returned (title, duration, sample url, vocal_id), the pagination mechanism, and the underlying GET /music/vocals endpoint.

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 packs routing, pagination, and return info into a compact block. It is dense and parenthetical, but nearly every clause carries load, so little is wasted.

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 paginated read with no output schema, the description supplies the return fields, pagination approach, account/mine semantics, sibling routing, and the endpoint. Nothing essential to correct invocation 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%, so baseline is 3. The description goes beyond the schema by framing mine as 'the voices you uploaded' and by tying vocal_id to downstream tools (create_song_with_lyrics, create_character), adding usage meaning the schema does not.

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 singing voices) and immediately differentiates from the sibling mureka_list_voices, which it names as handling speech voices. An agent can distinguish it from clone_voice, upload_vocal, and list_voices without opening any 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?

Explains the mine:true condition (uploaded voices) versus the default library, names the alternative mureka_list_voices for speech voices, and notes pagination via last_id. It stops short of an explicit 'when not to use' for other listing scenarios, but the routing context is clear.

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