Change narrator voice

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

Adds valuable behavioral context beyond the annotations: it is paid, preserves performance/lip-sync/background sound, and returns a served URL. Annotations only indicate mutability and non-destructiveness, so the description enriches the agent's expectations. It does not mention whether the operation is synchronous or returns a job ID, but the core behaviors are well disclosed.

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, zero fluff. The primary action is front-loaded, followed by usage guidance and a paid/return note. Every sentence earns its place and the description is easy to scan.

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 two straightforward parameters and no output schema, the description covers the key aspects: what it does, when to use it, cost, and return value. It omits any note about processing time or async behavior, which could be relevant given sibling tools like get_job, but for basic invocation the description is sufficient.

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?

Both parameters are fully described in the schema (100% coverage), including examples for voice and a default value. The tool description adds no additional parameter semantics beyond what the schema already provides, so the baseline score of 3 is appropriate.

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 action ('Swap the narration of a finished video into a different voice') and resource ('finished video'), and explicitly contrasts with dub_video for language translation. The description makes it unmistakable what this tool does and how it differs from a closely related sibling.

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 explicit usage guidance: 'Use when the user likes the video but wants a different narrator voice; use dub_video only for language translation.' This names the alternative and the condition for selection, leaving no ambiguity about when to pick this tool over its sibling.

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