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

Annotations already declare readOnlyHint=false, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavior: it costs credits, output is fixed at 5s/720p/audio, and the call is asynchronous, returning a task_id to poll with get_video. Missing only failure/timeout behavior or expected generation latency.

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 compact sentences, zero filler. The output spec and the text-only constraint are front-loaded, with the cost and the task_id/poll pattern trailing as secondary but essential facts.

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 tool with a fully documented schema, this covers everything an agent needs: what it produces, what it costs, that it is async, and which tool continues the flow. No output schema exists, yet the description still explains the return value (task_id).

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%, with prompt and aspect_ratio both fully described including the enum meanings, so the schema does the heavy lifting. The description adds only an implicit constraint ('text description only') and no syntax, length, or format detail beyond what the schema states. Baseline 3 applies.

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?

Names a specific verb and resource ('Generate a short video') and pins down the output envelope (5 seconds, 720p, with sound) plus the input modality ('from a text description only, no photo needed'). The 'no photo needed' clause directly separates it from the sibling animate_photo, so an agent can route without opening schemas.

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?

Gives clear conditions: use text only, no photo required, and expect a credit cost. It also names the follow-up path ('poll get_video'), which tells the agent this is step one of a two-call flow. It stops short of naming alternatives like create_image or animate_photo as explicit exclusions, or pointing to get_credits before spending.

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