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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds value by specifying that only 'public' voices accessible to the key are returned and by enumerating the returned fields, though it says nothing about result size, ordering, or pagination.

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 with zero filler; the capability and returned fields come first, and the follow-up action is placed at the end where it is most actionable.

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 no output schema, the description usefully compensates by naming the four returned fields, and the sole parameter is covered by the schema. It is nearly complete for a simple read tool, missing only ordering/pagination expectations.

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% and the single optional 'language' parameter is fully documented in the schema, including prefix-matching behavior and examples. The description adds nothing about the filter, so the baseline 3 applies.

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 verb and resource ('List the public VoiceHue voices a key can use') and names the exact fields returned (id, name, language, gender). It also distinguishes itself from its only sibling by telling the agent the output feeds 'text_to_speech'.

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?

'Pass a voice id to text_to_speech' makes the workflow role of this tool explicit — it is the discovery step before synthesis. It does not state any when-not conditions or edge cases (e.g., what to do with an empty list), so it stops short of full routing guidance.

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