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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds valuable behavior: the language filter performs a prefix match against base codes, so region tags like 'en-US' match nothing. This is beyond annotation coverage and helps the agent avoid failed queries.

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 sentences, zero fluff. The first sentence states the purpose and scope; the second adds filtering options and output highlights. Information is front-loaded and every clause earns its place.

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?

With only two optional parameters, full schema coverage, and annotations covering safety, the description is sufficient. It mentions output metadata, sampleUrl, and voice ID relevance to phone_call_create. No critical missing context for an agent to invoke correctly.

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% with rich descriptions, especially for language. The tool description only says 'filter by language or gender', which adds no meaning beyond the schema. The language parameter's prefix-matching detail is already in the schema, so the description itself does not enhance parameter understanding.

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 clearly states the tool lists AI voices for placing phone calls, specifying the verb (list), resource (voices), and purpose. It distinguishes from sibling tools like phone_call_list and phone_number_list by focusing on voice catalog rather than call records or numbers.

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 indicates the voice ID is needed for phone_call_create, implying the intended workflow. However, it does not explicitly state when not to use this tool or mention alternative tools for other contexts. It gives clear context but no formal exclusions.

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