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

Annotations declare only destructive=true, non-idempotent, non-read-only. The description adds material behavior the annotations cannot: it spends credits, is asynchronous and returns on dispatch rather than completion, enforces a dependency ordering around anchored recurring faces, and caps output per call with the overflow returned as remaining scenes. This is exactly the extra context the annotations leave out.

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 purpose, then cost/dispatch behavior, then the ordering rule. Mostly dense and useful, though the middle sequence ('Ask for the open wave, look at it, create_subject from the anchor, then the next') is compressed to the point of being cryptic.

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 high-complexity, credit-spending, async tool with an output schema present, the description covers the operational model an agent needs: cost, dispatch semantics, polling target, and ordering. The remaining gap is the undocumented reference/idempotency parameters rather than return values.

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 carry the burden. It explains quote (price the batch against balance without generating) and implies scenes, but references, reference_scenes (max 4), storyboard_id, and idempotency_key get no explanation at all — the agent is left guessing at the reference-object shape and the retry key.

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 concrete verb+resource ('Make the still pictures of the scenes you name') and pins it to a specific artifact type (scene stills) distinct from generate_image and animate_scenes. An agent can route to it 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?

Explicitly routes the workflow: dispatch then poll get_storyboard, use create_subject from the anchor still before the next wave, and use quote to price without producing. It also states the ordering gate (a scene is refused until its turn) and the concurrency cap, which tells the agent exactly when this call will and won't succeed.

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