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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds real behavioral detail beyond that: the spine selection rule (most shared narrative roles, or the one you name), passage scaling to exact duration, role-by-role alignment of the other references as alternatives, and a copy-to-role mapping. That is solid added context, though it stays silent on determinism of tie-breaking and on any limits when references conflict.

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 action and the reference count, then the spine mechanic, then the copy mapping, then the return contract - a sensible order with no filler sentences. It is dense and clause-heavy, approaching run-on in the middle, but each clause carries distinct 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?

With an output schema present, the description does not need to enumerate return fields, and naming the downstream consumers covers interoperability. For a 6-parameter tool with nested brief and style objects and zero schema descriptions, the missing style/aspect semantics is the main residual gap.

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 0% across 6 parameters, so the description must compensate and it only partly does: it explains references (1-5), spine (a name that overrides the automatic pick), duration ('scaled to your exact duration') and most brief substructures (message->hook, features->feature reveals in order, cta->call to action). It says nothing about style (background/foreground hex), aspect (16:9 vs 9:16), or what proof and problem map to, leaving half the surface undocumented.

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?

Opens with a specific verb and resource ('Plan one film from 1 to 5 chosen reference videos'), and explains the spine/reference relationship so the agent knows exactly what artifact is produced. It does not explicitly name the closest sibling (plan_structure or reference_brief) to contrast against, so differentiation is arrived at by inference rather than stated.

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?

Preconditions are implied (you need 1-5 chosen reference videos plus a brief) and downstream fit is spelled out ('critique_plan, beat_grid, music_brief and generation_prompts accept as is'), which is genuinely useful routing. However there is no explicit when-not guidance and no comparison to plan_structure or reference_brief, so the agent must guess which planning tool to pick when it has no references.

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