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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description is consistent with a safe read. It adds genuinely useful context beyond the annotations: the underlying model (Smart Turn v2), that the output is a probability, and a per-call cost of $0.003 USDC via x402 payment. Latency and rate-limit behavior are not covered.

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 compact clauses, front-loaded with the decision question the caller actually needs answered. Every sentence carries information (purpose, output, cost) with no filler.

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 output schema, the description correctly conveys the return (an end-of-turn probability) and adds the pricing model an agent must know before paying. It is nearly complete for a two-param tool; only the parameter-choice guidance 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 only 50%: audio_base64 carries a format spec while audio_url has no description. The description partially compensates by specifying 'the last few seconds of a caller's audio', but it never explains the audio_url vs audio_base64 choice or accepted formats for the URL path, so the gap is only partly bridged.

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: send caller audio, get end-of-turn detection with a probability. The opening question 'Has the speaker finished?' frames the exact job, and it is easily separable from transcribe/speak-style siblings. An agent knows what this does without opening the schema.

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 context for use ('so a voice agent replies at the right moment instead of interrupting') and timing guidance ('the last few seconds'). It does not name an alternative such as voice_session or turn, nor any when-not-to-use condition, so it stops short of full routing guidance.

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