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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so safety needs no restating. The description nonetheless adds real behavioral context: the upper-bound nature of the figure ('maximum', 'the most the render can cost'), the billing granularity (clip generation only), and the refund policy for failed renders.

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 short sentences with the core meaning front-loaded; the pricing ratio and refund caveat are parenthetically packed rather than sprawling. Minor redundancy between 'maximum credits' and the closing 'Returns the most the render can cost.'

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?

With no output schema, the description needs to say what comes back, and it does identify the return as the maximum possible cost. It is slightly thin on whether a breakdown or plain number is returned, but an agent has enough to call and interpret it correctly.

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 100% and all three parameters carry their own descriptions, so the schema already does the heavy lifting. The description only reinforces duration_seconds for the regenerate_scene case, adding no detail about scene_count or single_scene beyond what the schema states — the expected baseline of 3.

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 names a specific verb and resource — estimating the maximum credits a render will cost — and immediately qualifies the unit ('~1 credit per rendered second'). It is clearly distinguishable from the sibling mutation tools (create_video, regenerate_scene), though it never explicitly names what it is not.

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 a concrete routing rule: 'For regenerate_scene pass the chosen scenes' total duration,' which tells the agent exactly which value to supply in that workflow. There is no explicit statement of when not to call it or of alternative tools, keeping it short of a 5.

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