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

Annotations cover the mutation/cost profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), and the description adds valuable context beyond them: it returns an async job, is free of credits, and produces an editable film with no text layers. It stops short of describing job polling or failure behavior.

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 outcome, then qualifies editability and cost. Every sentence carries information, though the final clause about text layers is slightly tangential and could be folded in.

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 2-parameter mutation tool with no output schema, the description supplies the key facts an agent needs: async job return, credit cost, editability, prerequisite capture state, and the render hand-off. Job-lifecycle detail is the only notable omission.

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 coverage is 100% and the enum for 'aspect' is fully described in the schema, so the baseline is 3. The description adds only that the capture must be 'finished' and that the frame is 'chosen', which is marginal 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 ('Makes a 12-second launch film ... from a finished capture') with concrete scope (headline, button, picture, chosen frame). It also distinguishes itself from siblings by naming ugcfans_export_film as the renderer and clarifying the no-text-layers nature, setting it apart from ugcfans_set_film_words.

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?

Clear context: requires a 'finished capture', produces an editable film, and routes rendering to ugcfans_export_film. It does not explicitly state when-not to use it versus siblings like ugcfans_ad_to_film or ugcfans_make_site_sting, leaving some inference to the agent.

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