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

Annotations only declare readOnlyHint and openWorldHint; the description adds substantially more — that ElevenLabs entries carry preview URLs, that clones must be referenced by clone id, that clone limit and credit cost are returned, and that app-capable hosts render an interactive panel whose contents should not be echoed in the reply. That last point is non-obvious host-dependent behavior an agent would otherwise get wrong.

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?

Front-loaded with the core purpose, then layered with return categories, downstream usage, and a rendering caveat. The final panel instruction is comparatively long but carries non-obvious guidance, so it earns its place; the sentence structure is dense but readable.

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 input parameters and no output schema, the description carries the full burden of explaining returns, and it does so thoroughly — categories, identifier conventions, credit-related fields, and host rendering. An agent has everything needed to call it and to interpret and present the result 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?

The tool takes zero parameters, so the baseline is 4 per the rubric. The description does name the result field keys (presets, elevenV3Voices, clones, maxClones, cloneCreditCost), which helps with return interpretation, but there are no parameter semantics to clarify.

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 and goes further by enumerating the three voice categories returned (presets, elevenV3Voices, clones) plus the aggregate fields (maxClones, cloneCreditCost). It does not, however, distinguish itself from the sibling list_voiceover_voices, which an agent could easily confuse with this tool.

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?

Gives clear downstream context: voices returned here work as voice_id in create_voiceover and create_avatar_video, and change_voice specifically requires a cloned voice. It stops short of stating when to call this versus list_voiceover_voices, so no explicit alternative or exclusion is named.

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