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

Annotations already cover read-only, idempotent, non-destructive behavior. The description adds useful context about what is estimated (seconds and USD) and the billing basis (voice's per-second price), though it doesn't discuss approximation or error conditions.

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?

A single sentence front-loads the estimate, duration, cost, voice, and billing basis with no filler. Every clause contributes to understanding the tool's output.

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?

No output schema exists, so the description must convey return values; it does so by stating that it returns seconds of audio and USD cost. It omits how to obtain voiceId and any error behavior, leaving a minor completeness gap.

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 description ties both parameters to the estimate—script as spoken text and voice as the price basis. However, schema coverage is only 50%, with voiceId undocumented in the schema, and the description does not compensate with format, source, or constraints for voiceId.

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: estimate audio duration and USD cost for a script with a given voice. It clearly distinguishes the tool from the sibling lookup/help tools.

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?

Usage is implied as a pre-billing estimate, but the description does not explicitly say when to use this vs. siblings or how to obtain a valid voiceId. With get_voice/search_voices available, the lack of routing is a clear gap.

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