Generate a voiceover or music

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

Annotations indicate a mutating, non-idempotent operation (readOnlyHint=false, idempotentHint=false). The description adds important behavioral context beyond annotations: the tool spends credits, the price is queryable via fattly_list_models, and credits are refunded automatically on failure. It also discloses the returned mp3 link, providing useful operating context.

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 zero redundancy: the first establishes the core function and modes, the second the output, and the third the credit cost and refund behavior. Information is front-loaded and every sentence adds value.

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 tool with 4 parameters, 2 required, full schema coverage, and no output schema, the description is complete: it explains what the tool does, the two modes, the return format, and the cost/refund behavior. An agent has enough context to select and invoke the tool correctly without additional missing details.

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. The description reinforces the meaning of mode and text ('voiceover from text' vs 'music from a description') but adds no new parameter semantics beyond what the schema already documents. The refund and mp3-link details concern behavior, not parameters.

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?

Clearly states a specific verb and resource: 'Generates AI audio', with two distinct modes (speech voiceover from text, music from a description) and a concrete output (link to mp3). This differentiates it from sibling generation tools like fattly_generate_image and fattly_generate_video.

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?

Provides clear context for when to use the tool: when audio is needed, with the mode parameter selecting voiceover vs music. It also references fattly_list_models for pricing and mentions a refund on failure. It does not explicitly name sibling alternatives, but the audio-only scope and mode explanation make the intended usage obvious.

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