Generate a video clip from a project image

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

With no annotations, the description carries full burden. It reveals key behaviors: async operation returning a jobId, automatic resolution of imageUrl, and credit cost. This is valuable but lacks details on error handling, idempotency, or default values for unmentioned parameters.

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?

The description is three concise sentences, front-loading the core purpose and adding essential behavioral notes without any fluff. Every sentence earns its place.

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?

Given the tool's complexity (8 parameters, no output schema, no annotations), the description covers the main purpose and critical behaviors (async, cost, auto-resolve) but omits details on parameter defaults, motion types, and response format beyond the jobId. It is adequate but has clear gaps.

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 only 38%, and the tool description adds minimal parameter insight beyond noting that imageUrl auto-resolves. The description does not explain the meaning or impact of motion, resolution, aspectRatio, or customMotionPrompt, leaving a significant semantic gap.

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 clearly states the action: 'Animate one still project image into a video clip (Runway Gen-4).' It identifies the verb (animate/generate), the resource (video clip), and the source (project image), successfully distinguishing this from sibling tools like edit_image or render_movie.

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 description mentions the async pattern and polling requirement, but does not provide explicit guidance on when to use this tool over alternatives such as render_movie or add_timeline_overlay. Usage context is implied rather than clearly stated with when/when-not or alternatives.

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