Kokoro Text to Speech MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions that the output is an MP3 file and that upload to S3 is optional, which adds some context. However, it doesn't cover important aspects like rate limits, authentication requirements, error conditions, or what the returned dictionary contains. For a tool with 6 parameters and no annotation coverage, this is insufficient.

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?

The description is well-structured and appropriately sized. It starts with the core purpose, then lists parameters with clear explanations, and ends with return information. Every sentence earns its place, though the formatting with 'Args:' and 'Returns:' sections is slightly verbose but still efficient.

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?

Given the tool's complexity (6 parameters, no annotations, no output schema), the description is moderately complete. It excels at parameter documentation but lacks behavioral context and usage guidelines. The absence of an output schema means the description should ideally explain the return dictionary structure, which it doesn't. It's adequate but has clear gaps.

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 provides excellent parameter semantics beyond the input schema. With 0% schema description coverage, the description fully compensates by explaining each parameter's purpose, default values, and optionality. It clarifies that 'filename' is auto-generated if not provided and that 'upload_to_s3' depends on whether S3 is enabled. This adds significant value over the bare schema.

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 clearly states the tool's purpose: 'Convert text to speech using the Kokoro TTS service.' It specifies the verb ('convert') and resource ('text to speech'), and mentions the specific service. However, without sibling tools, it cannot demonstrate differentiation from alternatives, so it doesn't reach the highest score.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention any prerequisites, constraints, or typical use cases. The only contextual information is the service name (Kokoro TTS), but this doesn't help an agent decide when this tool is appropriate.

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