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

Annotations only cover safety hints (readOnlyHint=false, destructiveHint=false, openWorldHint=false); the description goes well beyond them with exact credit pricing (7/5s, 13/10s, +2 for scene), the side effect of scene-staging, the returned clip id, and non-obvious polling behavior. Prescriptive guidance on silent reactions ('mouth closed, no talking, an expression arc in beats') is unusual and valuable context.

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 what the tool does and its cost, and every sentence carries information (pricing, reaction guidance, return value, polling). The reaction-prompt advice and polling note are slightly interleaved with the core behavior, but there is little waste.

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?

An output schema exists, yet the description still flags that the clip id is returned and, more importantly, explains the self-polling player card so an agent does not misfire get_video. Cost, prerequisites, and mutation behavior are all covered for a complex zero-required-parameter, nested-object 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 coverage is 100%, so the baseline is 3, but the description adds real meaning: the credit cost attached to the scene parameter and the alternative between prompt and reaction. It leaves photo/scene interaction with image somewhat implicit, but exceeds what the schema alone conveys.

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: 'Animate a completed look into a short clip of the influencer.' The scene clause ('adding scene stages the look in a new place first') hints at its distinction from scene-replace siblings, but it never names create_clips, create_motion_clip, or create_scene_replace_clip, so an agent must infer which of the four clip creators applies.

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 concrete workflow guidance: 'Confirm with get_credits' as a prerequisite and an explicit when-not ('do not poll get_video when the card is showing'). However, it does not state when to choose this tool over the three sibling clip-creation tools, leaving the main routing decision to inference.

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