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

With no annotations provided, the description carries the full burden for behavioral disclosure, and it states 'Read-only' explicitly. It also describes the output as a catalogue, but does not detail format, pagination, or error behavior; still, this is adequate for a zero-parameter list operation.

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?

The description is a single, front-loaded sentence with no filler. It states what the tool returns, its purpose, and its safety profile without redundancy.

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 zero-parameter read-only list tool, the description is mostly complete: it names the resource, its purpose, and read-only nature. However, because there is no output schema, a bit more detail about the voice identifiers or fields returned would have made it fully self-sufficient.

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?

The tool has zero parameters and schema description coverage is 100%, so there are no parameter semantics to explain. The description's reference to set_agent_voice is contextually helpful but adds no parameter detail, matching the baseline for a no-parameter tool.

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 a specific verb and resource: it lists Retell voices, and identifies them as a catalogue for assignment via set_agent_voice. This clearly distinguishes it from sibling tools like create_agent or get_agent, and the 'Read-only' note reinforces its scope.

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 description implies when to use this tool: when you need available voices to assign through set_agent_voice. It does not explicitly discuss alternatives or exclusions, but for a simple list-only tool that context is sufficient.

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