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

Goes well past the annotations by disclosing that the scene is validated against authoring rules and auto-fixed before saving, that unspecified attributes are preserved on rewrite, and that each call costs 1 AI credit (refunded on failure). This contradicts nothing in the annotations and adds real invocation 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?

Front-loaded with the core action and the dual-mode distinction, then costs and permissions. It is a dense single paragraph, but nearly every clause carries decision-relevant information; only the permission sentence is fully redundant with structured data.

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, credit-consuming AI generation tool with no output schema, it covers cost, side effects, validation, and failure behavior. An agent has everything needed to decide and invoke 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 already 100%, so the baseline is 3; the description still adds meaning beyond it by explaining the sceneId branch's preservation behavior, the default insertion position, and the source of valid block values. Concrete instruction examples ('punchier, with the numbers counting up') further clarify intent.

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?

States a specific verb and resource ('AI director writes one scene') and cleanly splits the two modes: rewrite when sceneId is present, add when absent. It distinguishes itself from siblings by naming update_scene and list_video_blocks for adjacent needs.

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?

Explicitly routes the agent: 'For plain copy, timing or narration changes use update_scene instead (free and instant)', and points to list_video_blocks when a kit block is wanted. Both the when-to-use and when-not-to-use cases are covered.

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