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

With no annotations, the description still makes the read-only nature clear through 'List' and describes the returned fields. It does not mention auth, pagination, or rate limits, but for a simple static voice list the key behavioral trait, no mutation, is sufficiently conveyed.

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?

Two short sentences, front-loaded with the purpose and followed by the actionable next step. Every sentence carries information and there is no redundant phrasing.

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 simple list tool with no output schema, the description covers what is returned, the fields attached to each voice, and how to use the id. It is nearly complete, with only minor operational details such as auth or pagination left implicit.

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 100%, so the single api_key parameter is already documented in the schema. The description adds no further detail about that parameter, which is acceptable given the high coverage and baseline expectation.

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 uses a specific verb and resource: 'List the voices you can use on calls.' It also defines the returned attributes (gender, accent, personality), making the tool's purpose unmistakable and distinguishable from call-placement siblings.

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?

It explicitly ties the tool to call usage and names the downstream consumer: 'Pass the id as make_phone_call's voice.' That gives clear context, though it does not spell out when-not conditions or compare against another voice-selection path.

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