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

Annotations only cover the safety profile (non-read-only, non-destructive, non-idempotent, closed-world). The description adds genuinely new behavior: fixed 12s/8-scene output, text remaining editable, zero credit cost, and synchronous return of the film plus its first revision. That is substantial context beyond structured fields, though permission/auth requirements are not addressed.

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?

Three dense sentences front-load the core action and output spec, then add the sibling contrast and cost/return facts. Every sentence carries information with no filler.

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 no output schema, the description correctly compensates by stating the return ('the film and its first revision at once'), plus duration, scene count, editability, and cost. It does not cover async/job behavior, though the synchronous return framing largely addresses that for this creation tool.

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 all four parameters are already documented. The description only reinforces the node_ids source and the 'chosen frame' notion, and never mentions key_phrase, so it does little beyond the schema baseline.

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 (Makes) and precise resource (a 12-second, 8-scene film from chosen page parts), and ties node_ids to their source (ugcfans_get_capture). It explicitly differentiates itself from the sibling ugcfans_make_launch_film, so an agent can pick between them without opening either 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?

The contrast 'Unlike a launch film its page text stays as editable text, so ugcfans_set_film_words can change it' gives a real selection criterion against the launch-film sibling and names the downstream editing tool. It stops short of an explicit when-to-use/when-not statement, but the routing context is clear.

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