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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true), it discloses the async job model, the returned id and credits_charged, terminal statuses, and that results include downloads while wait helpers add exact_download_urls. It also states the pricing (0.1 credits per character, rounded up), the signed-URL preservation rule, and consent/anti-impersonation constraints — behavior the annotations cannot convey. It is weaker on what happens on failure/refund or whether credits are charged for failed jobs.

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 content is dense and largely earns its place, but the purpose statement is buried mid-paragraph behind a generic 'MCP guidance' preamble about the async job. The settings/constraints paragraph ("A listed model, resolution, duration or count...") is boilerplate-heavy and not specific to this tool, adding bulk without a corresponding voice-cloning detail.

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 mutating, nested-schema, async job tool, the description covers the full lifecycle: submission, cost model, polling vs. wait helper, result fields, file input conventions, and pre-flight checks against account constraints. An output schema exists, so it correctly avoids detailing return payload shapes and instead focuses on the workflow an agent must orchestrate.

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?

With schema coverage at 67%, the description usefully compensates for the least self-documenting parameter by explaining the allowed forms of audio_file_path (existing Magic Hour path vs. upload-URL response field vs. direct URL) and the pitfalls of public URLs. It also ties text length to cost (per character, rounded up), adding meaning beyond the prompt maxLength. Speed, language, and name are left entirely to the schema, which does document them well.

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 line "Clone a voice from an audio sample and generate speech" gives a specific verb and resource that an agent can act on. It implicitly separates this from sibling generation tools (e.g., ai_voice_generator_create_audio) by emphasizing cloning from a sample, but it never explicitly contrasts with that sibling, so it stops short of a 5.

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?

It explicitly routes post-submission behavior: call wait_for_audio_project with the returned id or poll GET /v1/audio-projects/{id} until complete/error/canceled. It also gives practical guidance for the *_file_path input (prefer the upload-URL endpoint when unsure; hotlinked URLs can fail) and tells the agent to read get_account_info before choosing settings. It does not explicitly state when to prefer this tool over ai_voice_generator_create_audio, which keeps it at 4.

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