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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely non-obvious behavior: the call is paid ($0.005 USDC via x402) and returns a WAV blob, which materially affects how an agent plans the call. It omits error behavior (e.g., over-length text) and payment failure modes.

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, capability first, then inputs and output, then cost. No filler and nothing buried; 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?

For a two-parameter tool with no output schema, the description covers input limits, output format, and pricing — enough to invoke correctly. Missing only edge-case behavior (over-length text, unsupported language handling) and how the x402 payment is settled.

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 50%: lang is documented in the schema, text is not. The description partially compensates by disclosing the 2000-character cap on text and restating the language codes. With half the parameters still bare in the schema, this only reaches baseline.

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 capability ('Text to speech') with concrete output format (WAV) and input limits, so the agent knows exactly what it produces. It does not differentiate itself from close siblings such as speak_pro or audio_speech, which appear to overlap in function.

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?

No statement of when to use this versus speak_pro, audio_speech, or voice_session. The only constraints given (2000 chars, language set) are input limits rather than selection guidance, so the agent must infer the use case from the name alone.

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