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

Annotations already mark this as a non-read-only, non-destructive, non-open-world write, so the safety profile is covered. The description adds real behavioral context on top: it is an async submit-and-poll operation ('do not wait here for the full render'), idempotencyKey is auto-generated, and omitting quoteId triggers an implicit quoting step (a hidden side-effect/cost). It does not cover failure or retry behavior, so not a 5.

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 then the workflow, which is the right order. It is slightly redundant — 'same plan as the site' appears twice and 'Submit and poll — do not wait here' overlaps with the earlier 'Poll get_character_film' — so a small amount of trimming is possible.

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?

An output schema exists, so return values need not be described, and the description supplies the full call sequence (quote → submit → poll → continue). For a 3-parameter async generation tool this is nearly complete; only error/retry handling on an ambiguous submit is left implicit.

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 100%, so the baseline is 3. The description's parameter notes ('this tool quotes the opening first when omitted', 'generated when omitted') effectively restate what the schema already says for quoteId and idempotencyKey, adding no new syntax, format, or constraint beyond the schema.

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 with scope: 'Start the Character Film opening (block 1, at most 8 seconds)'. It separates itself from the sibling quote_character_film (quoting) and continue_character_film (the rest of the film) inside the same sentence, so an agent can distinguish it without opening any 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?

Explicit when-to-use and what-to-do-next: poll get_character_film, do not block for the full render, and call continue_character_film once the opening completes. It also names the alternative to supplying quoteId (omit it and the tool quotes first), which is exactly the routing decision an agent must make.

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