Pixel-diff two .riv files

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

With no annotations provided, the description carries the full burden. It discloses forced identical output size, thresholding behavior, and the exact visualization color scheme (red/dim), adding context beyond the schema. It does not cover failure modes or requirements like matching artboards, but provides solid behavioral insight.

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 two sentences, front-loaded with the core action, and every clause adds value. There is no redundancy or fluff, making it highly concise and well-structured.

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 an 11-parameter tool with no output schema, the description explains the core behavior and return values but leaves background and stateMachine parameters unexplained. It gives a good baseline but does not fully document all configuration options, especially optional selectors.

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 45%, so the description compensates by clarifying that artboard, animation, and time parameters select the rendering context, width/height are forced to identical sizes, threshold controls matching strictness, and out specifies the PNG path. It does not explain background or stateMachine, but most parameters are implicitly covered.

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 tool renders two .riv files under identical conditions and computes a thresholded per-pixel visual diff, explicitly listing output contents (match rate, pixel count, diff PNG). The phrase 'visual diff' differentiates it from sibling tools like riv_diff and riv_ab_compare.

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 strongly implies usage for comparing visual output of two .riv files but does not explicitly state when to choose this tool over alternatives or provide exclusions. It lacks direct references to riv_diff or riv_ab_compare, so the guidance is implied rather than explicit.

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