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

With no annotations the description carries the full burden, and it does so well: it discloses the two output branches (ok:false lists what to fix; ok:true gives canvas/text-board layout instructions), that it returns each REF's real still, and even the Pro/free tier note. It omits permissions, rate limits, and error conditions, so it is not exhaustive.

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 moment of use, and nearly every clause adds actionable detail rather than restating the name. It is a dense wall of text with several run-on sentences that could be broken into a when-to-use line, an input-shape line, and an output-behavior line, so it is not maximally scannable.

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 very complex nested-schema tool with no output schema and no annotations, the description covers the workflow, both return branches, the direction-count logic, and layer conventions. The main omission is any guidance on the top-level technical params (aspect, bpm, fps, length_s) that shape the call.

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 low (30%), so the description must compensate; it does so strongly for `directions`, enumerating per-direction contents (logline, references with one job each, palette, type, sound, style frames, 3-30 panels with in/out seconds, shot size, camera move, transitions, layers) and the 'real' flag semantics. However, top-level parameters like bpm, fps, aspect, and length_s get no mention, leaving a real gap.

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 and resource ('storyboard the film', 'checks the timing and the REF ids') and explicitly names the sibling it consumes from and differentiates against ('the storyboard you drafted from plan_video'). An agent can tell this apart from plan_video and the other siblings without opening the schema.

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 context and workflow position ('Before anything is built', feed in the plan_video output, 1 direction for a fixed brief vs 2-4 when open) and an explicit retry rule ('fix it and call again') plus a post-condition ('Let the user pick a direction before you write any build prompt'). It stops short of explicitly contrasting similarly-named siblings such as check_render, so it is not a full when/when-not guide.

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