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

Annotations declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, but they say nothing about cost. The description adds genuinely new behavioral context: this is a paid operation that consumes the monthly allowance and is asynchronous (must be polled). It stops short of stating quota-exhaustion behavior or duration expectations.

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?

Three short sentences covering action, cost, and follow-up, with the core purpose front-loaded. No filler or redundancy.

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 a full input schema and an output schema present, the description does not need to explain parameters or return values. It covers the operation's cost and async nature, leaving only minor gaps such as auth requirements or what happens when the allowance is exhausted.

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 the schema already documents voice, script, and quoteId in detail (including the quoteId/voice mutual exclusion). The description adds no further parameter semantics, 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?

The description opens with a specific verb and resource: 'Start a paid Audio Lab narration,' which is clearly distinguishable from siblings like quote_audio_lab, generate_image_lab, and generate_video_lab. It does not explicitly name the sibling it is not, so it falls short of the top score, but the action 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?

It gives lifecycle guidance by naming the follow-up tool ('Poll get_audio_lab_generation until it finishes') and states the cost model ('Uses this month's generation allowance'). It lacks an explicit quote-first prerequisite or exclusions, which the schema hints at, so it is clear context but not a full when/when-not statement.

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