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

Annotations already declare a non-read-only, non-destructive, open-world operation, so the description's added note that it starts a background job and costs credits is real value beyond structured fields. It does not cover failure modes or credit-amount variability across models, which is the remaining gap.

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 tight sentences with the core action first and the async/cost caveat second. Nothing is redundant with the title or schema, and every clause carries information.

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 7-parameter, nested, async generation tool with an output schema and rich schema descriptions, the description covers the essential calling contract: image input, async job, credit cost, and the project-id handoff. Only the sibling differentiation for create_animation is missing.

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?

With 100% schema description coverage, the schema already documents every parameter, including the extensive per-model duration/resolution/audio tables. The description adds only the general notion of 'motion instructions and available model options' and does not clarify parameter syntax beyond the schema, so 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?

States a specific verb and resource: animates a supplied image into a video, with motion instructions and model options. This cleanly separates it from create_video_from_text and create_gif_or_short_video, though it doesn't explicitly name the nearby sibling create_animation, which could also involve still-image input.

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 sentence 'returns a project id for wait_for_video_project' gives a useful follow-up cue, but there is no guidance on when to choose this over create_animation or create_video_from_text, nor any prerequisites or exclusions. Usage is implied by the resource rather than stated.

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