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

With annotations already declaring destructive=true and readOnly=false, the description adds substantial context beyond them: it spends credit, it needs the write scope, the designed voice is kept on the character for reuse in later runs, and cloning requires the user's rights attestation. These are exactly the behavioral facts annotations cannot convey.

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-loads the highest-risk fact (SPENDS CREDIT) and then splits cleanly into the two parameter paths and the access requirement, plus the return summary. Dense but every clause carries information.

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?

Covers the mutation's cost, required scope, consent gating, persistence semantics, and even the return contents despite there being no output schema. For a 4-parameter mutation tool, nothing an agent needs before calling is missing.

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%, so the baseline is 3, but the description adds real meaning: `description` is casting direction persisted on the character, and `sampleMediaKey` cloning is gated on the `consent` attestation. It also notes the return payload (voice id, preview clip, cost).

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 ('gives an actor a voice') with the added scope that it SPENDS CREDIT. It clearly distinguishes two operating modes — designing from `description` versus cloning from `sampleMediaKey` — so an agent can tell what this tool does and how it differs from siblings like characters_list.

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?

Explains when each mode applies ('description designs one from casting direction' vs 'sampleMediaKey clones a real voice') and the condition `consent: true` for cloning. It does not name an explicit alternative tool or a when-not-to-use condition, so it falls short of a 5.

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