Text To Speech

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It clearly states the tool writes audio under NAN_OUTPUT_DIR (default ~/nan-mcp-output), does not overwrite existing files, and returns the saved path and size in bytes. It does not mention auth, rate limits, or other API caveats, but the write-safe behavior is a meaningful and useful disclosure.

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 sentences with no redundancy: the first states purpose and sibling distinction, the second gives a prerequisite, and the third covers output location, overwrite policy, and return value. Every sentence earns its place.

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?

The tool has 5 parameters (1 required), no output schema, and no annotations, so the description must carry context. It covers purpose, prerequisite, output location, overwrite behavior, and return value. Minor omissions like file extension handling and error conditions exist, but the rich schema plus this description are sufficient for a correct call.

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 baseline is 3. Each parameter already has a clear description, including the voice parameter with concrete examples. The description adds no additional parameter-level detail beyond the prerequisite to call list_voices, which is usage guidance rather than parameter semantics.

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 uses a specific verb ('Synthesize'), a clear resource ('speech from text'), and names the underlying engine ('kokoro (NaN API TTS)'). It also explicitly differentiates from the sibling 'speech_to_text' by saying it 'does the opposite', so an agent can confidently pick between the two.

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?

The description gives concrete, actionable guidance: call list_voices first to choose a voice id, and clarifies that speech_to_text is the opposite direction. This is an explicit alternative/routing instruction rather than leaving the agent to infer when to use the tool.

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