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

With destructiveHint=true, the description usefully discloses that re-invocation produces a different variation (implying the prior script is replaced) and that save-mode is free, plus the downstream storyboard-invalidation consequence. It does not explicitly confirm overwrite/reversibility of the existing script, so it stops short of full behavioral coverage.

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 dense sentences, front-loaded with the core action and mode-switching behavior, followed by the length parameter and the workflow constraint. No filler; every clause carries actionable information.

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 3-param generation tool with no output schema, the description covers generation vs save semantics, length limits, cost, and the storyboard dependency. It omits what the call returns (the generated script text or a confirmation), which an agent handling the result would benefit from knowing.

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 coverage is 67%: `script` and `project_id` are documented in the schema, but `target_seconds` is not. The description compensates by explaining that target_seconds sets length within 10–120s and that trial accounts are more restricted — meaning beyond the schema's bare min/max bounds.

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 states a specific verb+resource ('writes the voiceover script from the brief') and covers both operating modes: generative (no script passed) and save-mode (script passed). It is easy to tell apart from sibling generate_storyboard, which it explicitly references via the storyboard dependency.

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 gives clear operating context: each repeated call yields a different variation, passing `script` switches to save-mode, and changing a script after a storyboard forces a storyboard regeneration. It stops short of naming an explicit alternative tool to use instead, so it lacks the when-not/alternative routing that would merit a 5.

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