diff_images

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does explain the diff visualization (desaturation, red highlights) and scaling behavior, but it omits what happens to the composite output—where it is saved, whether it is returned, or any side effects. This is a notable 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?

The description is compact and well-structured, with two clear sentences explaining the behavior followed by a concise parameter list. Every sentence adds meaningful information, and there is no redundancy or extraneous detail.

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?

The description covers input handling and processing behavior, but it lacks information about the output format, destination, or return value. Since there is no output schema and no annotations, this missing context leaves an agent uncertain about what to do with the result.

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?

Although the JSON schema provides no parameter descriptions, the tool description explicitly defines each parameter: image_path_a and image_path_b as input paths, threshold as the pixel-difference cutoff (0-255), and tile_size as the longest panel side. This fully compensates for the schema's lack of descriptions.

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 states a specific verb ('Compare') and resource ('two images') and clearly distinguishes the tool by detailing the 3-panel composite output with A, B, and Diff panels. This makes the tool's purpose unambiguous and differentiates it from siblings like compare_reference_image.

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 explains how the diff is computed and how images are scaled, but it does not state when to use this tool versus alternatives such as compare_reference_image or get_viewport_screenshot. There is no explicit guidance on appropriate use cases or prerequisites.

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