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

With no annotations, the description carries the full burden. It usefully discloses that the output is a URL to generated audio and imposes a content rule (numbers spelled out for non-English), but says nothing about rate limits, authentication, persistence/lifetime of the audio URL, or whether synthesis is billed.

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 with zero waste; purpose and return value are front-loaded before the formatting caveat.

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?

It correctly explains the return value in the absence of an output schema and gives one correctness rule, but with no annotations the remaining behavioral gaps (permissions, limits, audio longevity) leave the definition only partially complete for a synthesis tool.

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?

At 67% schema coverage, the schema already documents lang and voice values; the description adds one genuine cross-parameter rule (number formatting depends on the chosen language). It does not explain valid voice ids beyond the schema example or note the 500-character text limit.

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 (turn text into speech) plus the useful outcome (returns a URL to the audio). It is clearly distinct from the reporting siblings list_voices and search_phrases, though it never names or contrasts them explicitly.

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?

There is no explicit when-to-use guidance, no prerequisites (auth, quota), and no mention of when to prefer search_phrases or list_voices as a precursor. Usage is only implied by the verb.

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