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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds ordering behavior not in the annotations ('by engine, best first'), which directly tells the agent the first entry is the recommended voice — a real selection cue beyond structured fields.

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 scope and ordering rule, then the hand-off to generate_speech. No filler.

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?

An output schema exists, so return-field explanations are unnecessary, and annotations cover the safety profile. The description supplies grouping/ordering and the cross-tool link, which is enough for a zero-parameter listing tool, though it doesn't hint at list size or refresh behavior.

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 takes zero parameters, so the baseline is 4. The description correctly adds no parameter detail because there is nothing to document; the mention of `id` refers to a field of the returned voices, not an input.

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 resource ('voices') and scope ('All voices by engine'), which is meaningfully more than a restatement of the name. It also names the downstream consumer (generate_speech), so an agent can place it in the workflow, though it doesn't explicitly contrast with any sibling.

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?

Guidance is about what to do with the output ('Pass a voice `id` (and its engine) to generate_speech'), which is useful routing, but there is no explicit when-to-call-this-tool statement. Usage is only implied, and no exclusions or alternatives are given.

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