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

Annotations already declare the mutation profile (readOnlyHint=false, openWorldHint=true, non-idempotent, non-destructive). The description's contribution beyond them is the plan-tier gate and the external-URL dependency, which is genuine but thin; it does not say that each call produces a new voice, whether it costs credits, or how long it takes.

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 padding: the action and its input source come first, and the eligibility constraint follows. Nothing is repeated from the schema or annotations in a wasteful way.

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 low-complexity, three-parameter mutation with an output schema and full annotation coverage, the description covers what the tool does, its input source, and an access prerequisite. Remaining gaps (cost/credits, synchronicity of the clone) are modest, and return values are handled by the output schema.

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 all three parameters are already documented, and the description only echoes the 'public sample URL' and 'custom voice' semantics. The optional 'description' parameter is not mentioned at all, so no meaning is added beyond the schema.

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 + resource ('Clone a custom voice') and names the input source ('public sample URL'), which clearly separates it from list_voices, create_character and other siblings. It stops short of explicitly naming an alternative, but the operation is unambiguous.

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?

Adds a real precondition ('Requires an Elite plan or better on Revid') that helps an agent decide whether it can be called at all. It gives no guidance on when to clone vs. upload or create a character, no note on sample-audio requirements beyond 'public', and no indication of whether cloning is asynchronous or consumes credits.

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