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

Annotations already declare destructiveHint=true, openWorldHint=true, idempotentHint=false and readOnlyHint=false, so the safety profile is covered. The description adds almost nothing beyond that: it does not say this starts a generation job whose result must be fetched with get_generation, gives no cost/time expectations, and does not warn about repeat/non-idempotent calls beyond what the annotations imply.

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?

Two sentences, front-loaded with the trigger condition and free of filler. The second sentence is largely redundant with the schema's duration constraints, but the overall size is appropriate.

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?

Seven parameters with nested image objects and a video generation side effect make this a complex tool, and an output schema exists to cover return values. The description still omits the most important operational context for an agent: that this is a long-running, non-idempotent generation whose output must be retrieved separately, and how the start/end image parameters relate to the four alternate URL form fields.

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%, including per-parameter notes on base64 passing, the 5/10-second enum, and image object structure, so the schema carries the parameter burden. The description's mention of style and 5- or 10-second duration merely restates what the schema already documents, adding no format or selection guidance.

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?

The description gives a specific verb and resource: an animated transformation from a start image to an end image. It is distinguishable from siblings like create_house_tour or create_video_walkthrough by the two-endpoint transition framing, though it never names those siblings explicitly.

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?

'Use when the user wants an animated transformation...' gives a clear trigger condition, which is better than nothing. However, there is no guidance on when NOT to use it (e.g. versus create_video_walkthrough), and no mention of prerequisites such as having both images attached or how the style is chosen.

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