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

With no annotations provided, the description carries the full burden of disclosing behavioral traits. It only restates the action ('set') and lists fields; it does not explain whether unspecified settings are reset, whether this is a partial or full update, what permissions are required, or what side effects occur.

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 compact: two sentences, front-loaded with the core settings and a directly useful prerequisite. No filler or redundant restatement of schema fields.

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 mutation with no annotations, no output schema, and five undocumented parameters, the description leaves too much to inference. The list_retell_voices prerequisite is valuable, but the agent still lacks enough context about id usage, valid values, and overwrite/merge behavior to reliably invoke the 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?

Schema description coverage is 0%, so the description must compensate, but it only gives an example for voice_type and mentions 'backchannel' which is not present in the schema. It does not clarify id semantics, language format, speed/temperature units, or the confusing 'speed'/'temperature' vs speech_speed/voice_temperature naming.

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?

Description uses a specific verb and resource ('Set agent voice settings') and enumerates the exact setting fields, making the tool's function unmistakable. It is clearly differentiated from siblings like list_retell_voices and set_agent_avatar_from_url.

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 gives a clear, actionable prerequisite: call list_retell_voices first to see available voice options. It does not explicitly mention when not to use the tool or contrast with alternatives like update_agent, but the context is clear enough for an agent.

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